£EPA
United States
Environmental Protection
Agency
Solid Waste and Emergency Response (5102W)
Innovative Site
Remediation
Technology
Solvent/Chemical Extraction
Volume 5
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INNOVATIVE SITE
REMEDIATION TECHNOLOGY
SOLVENT/CHEMICAL
EXTRACTION
One of an Eight-Volume Series
Edited by
William C. Anderson, P.E., DEE
Executive Director, American Academy of Environmental Engineers
1995
Prepared by WASTECH*, a multiorganization cooperative project managed
by the American Academy of Environmental Engineers® with grant assistance
from the U.S. Environmental Protection Agency, the U.S. Department of
Defense, and the U.S. Department of Energy.
The following organizations participated in the preparation and review of
this volume:
i [ASCE]
fe. "^ Air & Waste Management \/ American Society of
*^?nr Association \/4> Civil Engineers
P.O. Box 2861 345 East 47th Street
Pittsburgh, PA 15230 New York, NY 10017
American Academy of p mM, Hazardous Waste Action
Environmental Engineers® SSL Coalition
130 Holiday Court, Suite 100 1015 15th Street, N.W., Suite 802
Annapolis, MD 21401 Washington, D.C. 20005
Water Environment
Federation
601 Wythe Street
Alexandria, VA 22314
Published under license from the American Academy of Environmental
Engineers®. © Copyright 1995 by the American Academy of Environmental
Engineers®.
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Library of Congress Cataloging in Publication Data
Innovative site remediation technology/ edited by William C. Anderson
160 p. 15.24 x 22.86cm.
Includes bibliographic references.
Contents: -- [2] Chemical treatment — [3] Soil washing/soil flushing — [4]
Stabilization/solidification — [5] Solvent/chemical extraction — [6] Thermal
desorption -- [7] Thermal destruction — [8] Vacuum vapor extraction
1. Soil remediation. I. Anderson, William, C., 1943- .
II. American Academy of Environmental Engineers.
TD878.I55 1994 628.5'5 93-20786
ISBN 1-883767-02-4 (v. 2) ISBN 1-883767-06-7 (v. 6)
ISBN 1-883767-03-2 (v. 3) ISBN 1-883767-07-5 (v. 7)
ISBN 1-883767-04-0 (v. 4) ISBN 1-883767-08-3 (v. 8)
ISBN 1-883767-05-9 (v. 5)
Copyright 1995 by American Academy of Environmental Engineers. All Rights Reserved.
Printed in the United States of America. Except as permitted under the United States
Copyright Act of 1976, no part of this publication may be reproduced or distributed in any
form or means, or stored in a database or retneval system, without the prior written
permission of the American Academy of Environmental Engineers.
The material presented in this publication has been prepared in accordance with
generally recognized engineering principles and practices and is for general
information only. This information should not be used without first securing
competent advice with respect to its suitability for any general or specific applica-
tion.
The contents of this publication are not intended to be and should not be
construed as a standard of the American Academy of Environmental Engineers or of
any of the associated organizations mentioned in this publication and are not
intended for use as a reference in purchase specifications, contracts, regulations,
statutes, or any other legal document.
No reference made in this publication to any specific method, product, process,
or service constitutes or implies an endorsement, recommendation, or wairanty
thereof by the American Academy of Environmental Engineers or any such
associated organization.
Neither the American Academy of Environmental Engineers nor any of such
associated organizations or authors makes any representation or warranty of any
kind, whether express or implied, concerning the accuracy, suitability, or utility of
any information published herein and neither the American Academy of Environ-
mental Engineers nor any such associated organization or author shall be responsible
for any errors, omissions, or damages arising out of use of this informalicn.
Book design by Lori Imhoff
Printed in the United States of America
WASTECH and the American Academy of Environmental Engineers are trademarks of the American
Academy of Environmental Engineers registered with the U.S. Patent and Trademark Office.
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CONTRIBUTORS
This monograph was prepared under the supervision of the WASTECH®
Steering Committee. The manuscript for the monograph was written by a task
group of experts in solvent/chemical extraction and was, in turn, subjected to two
peer reviews. One review was conducted under the auspices of the Steering Commit-
tee and the second by professional and technical organizations having substantial
interest in the subject.
PRINCIPAL AUTHORS
James R. Donnelly, QEP Task Group Chair
Director of Environmental Services & Technologies
Davy International
Robert Ahlert, Ph.D., P.E., DEE
Distinguished Professor
Rutgers University
Richard J. Ayen, Ph.D.
Vice President & General Manager
Clemson Technical Center
Rust Federal Services Inc.
Sharon R. Just, P.E.
Environmental Engineer
Engineering-Science, Inc.
Mark C. Meckes
Physical Scientist
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
REVIEWERS
The panel that reviewed the monograph under the auspices of the Project
Steering Committee was composed of:
Richard A. Conway, P.E., DEE, Chair
Union Carbide Corporation
Wayne M. Kachel, Ph.D., P.E.
Martin Marietta Corporation
Peter B. Lederman, Ph.D., P.E.,
DEE, P.P.
Center for Environmental Engineering
& Science
New Jersey Institute of Technology
Robert B. Pojasek Ph.D.
Corporate Vice President, Environmental
Programs
GEI Consultants, Inc.
Kamalesh Sirkar, Ph.D.
Professor of Chemical Engineering
Sponsored Chair
New Jersey Institute of Technology
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STEERING COMMITTEE
Frederick G. Pohland, Ph.D., P.E., DEE
Chair
Weidlein Professor of Environmental
Engineering
University of Pittsburgh
Doniy Adriano, Ph.D.
Professor and Head
Biogeochemical Ecology Division
The University of Georgia
Representing, Soil Science Society of
America
William C. Anderson, P.E., DEE
Project Manager
Executive Director
American Academy of Environmental
Engineers
Colonel Frederick Boecher
Director of Risk Management
Chemical and Biological Defense
Command
U.S. Army
Representing, American Society of Civil
Engineers
Paul L. Busch, Ph.D., P.E., DEE
President and CEO
Malcolm Pirnie, Inc.
Representing, American Academy of
Environmental Engineers
Richard A. Conway, P.E., DEE
Senior Corporate Fellow
Union Carbide Corporation
Chair, Environmental Engineering
Committee
EPA Science Advisory Board
George Coyle
Division of Technical Innovation
Office of Technical Integration
Environmental Education Development
U.S. Department of Energy
Timothy B. Holbrook, P.E.
Engineering Manager
Groundwater Technology, Inc.
Representing, Air & Waste Management
Association
Walter W. Kovalick, Jr., Ph.D.
Director, Technology Innovation Office
Office of Solid Waste and Emergency
Response
U.S. Environmental Protection Agency
Joseph F. Lagnese, Jr., P.E., DEE
Private Consultant
Representing, Water Environment
Federation
Peter B. Lederman, Ph.D., P.E., DEE, P.P.
Center for Env. Engineering & Science
New Jersey Institute of Technology
Representing, American Institute of
Chemical Engineers
Raymond C. Loehr, Ph.D., P.E., DEE
H.M. Alharthy Centennial Chair and
Professor
Civil Engineering Department
University of Texas
Timothy Oppelt
Director, Risk Reduction Engineering
Laboratory
U.S. Environmental Protection Agency
David Patterson
Senior Technical Analyst
Waste Policy Institute
Representing, U.S. Department of Defense
George Pierce, Ph.D.
Editor-in-Chief
Journal of Microbiology
Manager, Bioremediation Technology
Development
Cytec Industries
Representing, Society of Industrial
Microbiology
Peter W. Tunnicliffe, P.E., DEE
Senior Vice President
Camp Dresser & McKee, Incorporated
Representing, Hazardous Waste Action
Coalition
Charles O. Velzy, P.E., DEE
Private Consultant
Representing, American Society of
Mechanical Engineers
Walter J. Weber, Jr., Ph.D., P.E., DEE
Earnest Boyce Distinguished Professor
University of Michigan
Representing, Hazardous Waste Research
Center
IV
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REVIEWING ORGANIZATIONS
The following organizations contributed to the monograph's review and
acceptance by the professional community. The review process employed by each
organization is described in its acceptance statement. Individual reviewers are, or
are not, listed according to the instructions of each organization.
Air & Waste Management
Association
The Air & Waste Management
Association is a nonprofit technical and
educational organization with more than
14,000 members in more than fifty
countries. Founded in 1907, the
Association provides a neutral forum
where all viewpoints of an environmen-
tal management issue (technical,
scientific, economic, social, political,
and public health) receive equal
consideration.
This worldwide network represents
many disciplines: physical and social
sciences, health and medicine, engineer-
ing, law, and management. The
Association serves its membership by
promoting environmental responsibility
and providing technical and managerial
leadership in the fields of air and waste
management. Dedication to these
objectives enables the Association to
work towards its goal: a cleaner
environment.
Qualified reviewers were recruited
from the Waste Group of the Technical
Council. It was determined that the
monograph is technically sound and
publication is endorsed.
The lead reviewer was:
Paul Lear
OH Materials, Inc.
American Society of Civil
Engineers
Qualified reviewers were recruited
from the Environmental Engineering
Division of ASCE and formed a Sub-
committee on WASTECH*. The mem-
bers of the Subcommittee have
reviewed the monograph and have
determined that it is acceptable for
publication.
The reviewers were:
Cecil Lue-Hing, Sc.D., P.E.
Metropolitan Water Reclamation
District of Greater Chicago
David T. Lordi, Ph.D.
Metropolitan Water Reclamation
District of Greater Chicago
David R. Zenz, Ph.D., P.E.
Metropolitan Water Reclamation
District of Greater Chicago
Hazardous Waste Action
Coalition
The Hazardous Waste Action Coali-
tion (HWAC) is an association dedi-
cated to promoting an understanding of
the state of the hazardous waste practice
and related business issues. Our mem-
ber firms are engineering and science
firms that employ nearly 75,000 of this
country's engineers, scientists, geolo-
gists, hydrogeologists, toxicologists,
chemists, biologists, and others who
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solve hazardous waste problems as a
professional service. HWAC is pleased
to endorse the monograph as technically
sound.
The lead reviewer was:
James D. Knauss, Ph.D.
Shield Environmental
Associates, Inc.
Water Environment
Federation
The Water Environment Federa-
tion is a nonprofit educational orga-
nization composed of member and
affiliated associations throughout the
world. Since 1928, the Federation
has represented water quality spe-
cialists including engineers, scien-
tists, government officials, industrial
and municipal treatment plant opera-
tors, chemists, students, academic
and equipment manufacturers, and
distributors.
A qualified reviewer was re-
cruited from the Federation's Hazard-
ous Wastes Committee.
It has been determined that the
document is technically sound and
publication is endorsed.
The reviewer was:
James A. Kent, Ph.D., P.E.
Chemical Engineering Consultant
vi
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ACKNOWLEDGMENTS
The WASTECH® project was conducted under a cooperative agreement
between the American Academy of Environmental Engineers® and the Office
of Solid Waste and Emergency Response, U.S. Environmental Protection
Agency. The substantial assistance of the staff of the Technology Innovation
Office was invaluable.
Financial support was provided by the U.S. Environmental Protection
Agency, Department of Defense, Department of Energy, and the American
Academy of Environmental Engineers®.
This multiorganization effort involving a large number of diverse profes-
sionals and substantial effort in coordinating meetings, facilitating communica-
tions, and editing and preparing multiple drafts was made possible by a
dedicated staff provided by the American Academy of Environmental Engi-
neers® consisting of:
Paul F. Peters
Assistant Project Manager & Managing Editor
Karen M. Tiemens
Editor
Susan C. Zarriello
Production Manager
J. Sammi Olmo
Project Administrative Manager
Yolanda Y. Moulden
Staff Assistant
I. Patricia Violette
Staff Assistant
vii
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VIII
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TABLE OF CONTENTS
CONTRIBUTORS Hi
ACKNOWLEDGMENTS vii
LIST OF TABLES xv
LIST OF FIGURES xvii
1.0 INTRODUCTION 1.1
1.1 Solvent/Chemical Extraction 1.1
1.2 Development of the Monograph 1.2
1.2.1 Background 1.2
1.2.2 Process 1.3
1.3 Purpose 1.4
1.4 Objectives 1.5
1.5 Scope 1.5
1.6 Limitations 1.6
1.7 Organization 1.7
2.0 PROCESS SUMMARY 2.1
2.1 Identification of Processes 2.1
2.2 Scientific Basis 2.2
2.3 Process Description 2.3
2.3.1 Basic Extractive Sludge Treatment Process 2.3
2.3.2 CF Systems 2.4
2.3.3 Carver-Greenfield Process 2.6
IX
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Table of Contents
2.3.4 Extraksol Process 2.7
2.3.5 Low-Energy Extraction Process 2.8
2.3.6 NuKEM Development Process 2.9
2.3.7 Soil Restoration Unit 2.10
2.4 Potential Applications 2.11
2.4.1 Basic Extractive Sludge Treatment Process 2.12
2.4.2 CF Systems 2.12
2.4.3 Carver-Greenfield Process 2.12
2.4.4 Extraksol Process 2.12
2,4.5 Low-Energy Extraction Process 2.13
2.4.6 NuKEM Development Process 2.13
2.4.7 Soil Restoration Unit 2.13
2.5 Process Evaluation 2.13
2.5.1 Levels of Contaminant Removal 2.13
2.5.2 Status of Development 2.14
2.5.3 Secondary Environmental Impacts 2.14
2.5.4 Costs 2.15
2.6 Limitations 2.15
2.6.1 Site/Matrix Considerations 2.15
2.6.2 Residue Treatment 2.15
2.6.3 Process Risks 2.16
2.6.4 Reliability 2.16
2.7 Technology Prognosis 2.16
3.0 PROCESS IDENTIFICATION AND DESCRIPTION 3.1
3.1 Identification of Processes 3.1
3.2 Scientific Basis 3.3
3.3 Process Description 3.6
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Table of Contents
3.4 Status of Development 3.8
3.5 Design Data 3.8
3.6 Pre- and Posttreatment 3.10
3.7 Environmental Impact 3.11
3.8 Basic Extractive Sludge Treatment Process 3.13
3.8.1 Description 3.13
3.8.2 Status of Development 3.15
3.8.3 Design Data 3.16
3.8.4 Pre- and Posttreatment 3.16
3.8.5 Operational Considerations 3.18
3.8.6 Environmental Impacts 3.18
3.9 CF Systems 3.19
3.9.1 Description 3.19
3.9.2 Status of Development 3.21
3.9.3 Design Data 3.22
3.9.4 Pre- and Posttreatment 3.23
3.9.5 Operational Considerations 3.24
3.9.6 Environmental Impacts 3.26
3.10 Carver-Greenfield Process 3.26
3.10.1 Description 3.26
3.10.2 Status of Development 3.30
3.10.3 Design Data 3.31
3.10.4 Pre- and Posttreatment 3.33
3.10.5 Operational Considerations 3.34
3.10.6 Environmental Impacts 3.35
3.11 Extraksol Process 3.35
3.11.1 Description 3.35
XI
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Table of Contents
3.11.2 Status of Development 3.37
3.11.3 Design Data 3.39
3.11.4 Pre- and Posttreatment 3.39
3.11.5 Operational Considerations 3.40
3.11.6 Environmental Impacts 3.40
3.12 Low-Energy Extraction Process 3.40
3.12.1 Description 3.40
3.12.2 Status of Development 3.43
3.12.3 Design Data 3.43
3.12.4 Pre- and Posttreatment 3.45
3.12.5 Operational Considerations 3.46
3.12.6 Environmental Impacts 3.46
3.13 NuKEM Development Process 3.47
3.13.1 Description 3.47
3.13.2 Status of Development 3.50
3.13.3 Design Data 3.50
3.13.4 Pre-and Posttreatment 3.51
3.13.5 Operational Considerations 3.52
3.13.6 Environmental Impacts 3.53
3.14 Soil Restoration Unit 3.53
3.14.1 Description 3.53
3.14.2 Status of Development 3.54
3.14.3 Design Data 3.56
3.14.4 Pre- and Posttreatment 3.56
3.14.5 Operational Considerations 3.58
3.14.6 Environmental Impacts 3.58
XII
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Table of Contents
4.0 POTENTIAL APPLICATIONS 4.1
4.1 Basic Extractive Sludge Treatment Process 4.1
4.2 CF Systems 4.2
4.3 Carver-Greenfield Process 4.3
4.4 Extraksol Process 4.4
4.5 Low-Energy Extraction Process 4.5
4.6 NuKEM Development Process 4.6
4.7 Soil Restoration Unit 4.6
5.0 PROCESS EVALUATION 5.1
5.1 Levels of Removal of Contaminants 5.1
5.2 Status of Development 5.2
5.3 Costs 5.2
6.0 LIMITATIONS 6.1
6.1 Site/Matrix Considerations 6.1
6.2 Residue Treatment 6.2
6.3 Process Risks 6.3
6.4 Reliability 6.3
7.0 TECHNOLOGY PROGNOSIS 7.1
APPENDICES
Vendor Contacts A.I
Emerging Processes B.I
Carver-Greenfield Process C. 1
Low-Energy Extraction Process (LEEP®) D. 1
NuKEM Development (NKD) Processes E. 1
XIII
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LIST OF TABLES
Table Title Page
3.1 Design Information 3.3
3.2 Status of Development^ 3.9
3.3 Summary of Pretreatment Requirements 3.10
3.4 CF Systems — Commercial System 3.22
3.5 CF Systems — Pilot Plant Data 3.23
4.1 Potential Applications Commercial Solvent/Chemical
Extraction Processes 4.2
5.1 Cost Comparison 5.3
B.I Bench Scale & Promising SCE Processes B.2
C.I Carver-Greenfield Site Demonstration C.4
C.2 Carver-Greenfield Site Demonstration: Oil Parameters C.6
C.3 Carver-Greenfield Site Demonstration: Average
Compositions by Weight Percent C.8
C.4 Carver-Greenfield Cost Analysis Summary C.9
C.5 Carver-Greenfield: Refinery Slop Oil Sample Composition
by Weight Percent C.10
C.6 Carver-Greenfield: Petroleum Sludge C.ll
C.7 Carver-Greenfield: Commercial Plant C.13
D.I LEEP Leaching Schemes D.2
D.2 LEEP Residual Soil Analyses After 10th Stage of Leaching
With Various Solvents D.3
D.3 LEEP Multistage PCB Leaching Results From Clay D.4
D.4 LEEP Base Neutral (Semivolatile) Leaching: Industrial
Landfill D.5
xiv
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List of Tables
Table Title Page
D.5 LEEP PCBs Leaching: Industrial Landfill D.6
D.6 LEEP Semivolatile Organic Compounds Leaching:
Refinery Sludges D.7
D.7 LEEP Oil and Grease Leaching: Refinery Sludges D.8
E. 1 NKD Process: Properties of Test Soils E.2
E.2 NKD Process: Particle Size Distribution of Selected
Test Soils E.2
E.3 Batch Extraction Performance of NKD Soil Washing
Process E.3
E.4 Characteristics of two Refinery Feedstocks E.4
E.5 Fate of Organics in Pilot-Scale Treatment of API
Separator Sludge E.5
E.6 Leachability of Metals in Samples of Pilot Scale
Processed API Separator Solids E.6
xv
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LIST OF FIGURES
Figure Title Page
3.1 Solvent/Chemical Extraction — Simplified Process Flow 3.7
3.2 B.E.S.T. Process Schematic 3.14
3.3 CF Systems Solvent Extraction Unit Process Diagram 3.20
3.4 Carver-Greenfield Process Schematic 3.28
3.5 Extraksol™ Process Simplified Process Schematic 3.36
3.6 LEEP® Flow Schematic 3.41
3.7 NKD Process Schematic — Contaminated Soils 3.48
3.8 NKD Process Schematic — Oily Waste 3.49
3.9 Terra-Kleen Soil Restoration Unit Process Schematic 3.54
B.I ChemWaste APES Flow Schematic B.3
B.2 Phoenix Contex Process B.4
B.3 Davy R&D RIP/CIP Process B.6
B.4 Martin Marietta Soilex Process Flow Schematic B.8
xvi
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Chapter 1
I
INTRODUCTION
This monograph on solvent/chemical extraction (SCE) is one of a series
of eight on innovative site and waste remediation technologies that is the
culmination of a multiorganization effort involving more than 100 experts
over a two-year period. It provides the experienced, practicing professional
guidance on the application of innovative processes considered ready for
full-scale application. Other monographs in this series address
bioremediation, chemical treatment, soil washing/soil flushing, stabiliza-
tion/solidification, thermal desorption, thermal destruction, and vacuum
vapor extraction.
1.1 Solvent/Chemical Extraction
Solvent/chemical extraction is an ex situ separation and concentration
process in which a nonaqueous liquid reagent is used to remove organic
and/or inorganic contaminants from wastes, soils, sediments, sludges, or
water. The process is based on well-documented chemical equilibrium
separation techniques utilized in many industries such as oil extraction from
soy beans, supercritical decaffeination of coffee, and separation of copper
from leaching fluids.
Solvent/chemical extraction can be differentiated from soil washing in
that soil washing1 involves the use of dilute aqueous solutions of detergents
or chelating agents to remove contaminants through desorption, abrasion,
and/or physical separation, whereas SCE relies on the action of concen-
trated chemical agents.
1 . See the monograph in this series, Innovative Site Remediation Technology: Soil
Washing/Soil Flushing—Ed.
1.1
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Introduction
Solvent/chemical extraction typically produces a treated fraction and a
concentrated contaminated fraction, which requires further treatment to
recover, destroy, or immobilize the contaminants. It may concentrate con-
taminants by a factor as high as 10,000:1, thereby significantly reducing the
volume of material requiring further treatment or producing a concentrated
stream for materials recovery.
The authors classified SCE technologies as follows:
• full-scale commercial or field-tested;
• bench-scale tested; and
• insufficient data available for evaluation.2
Full-scale commercial and field-tested processes are addressed in the
monograph proper. Processes demonstrated at the bench-scale level that the
authors deemed to warrant review are briefly addressed in Appendix B.
Technologies where insufficient data were available are listed in Section 2.1
and 3.1 but are not discussed.
/. 2 Development of the Monograph
1.2.1 Background
Acting upon its commitment to develop innovative treatment technolo-
gies for the remediation of hazardous waste sites and contaminated soils
and groundwater, the U.S. Environmental Protection Agency (EPA) estab-
lished the Technology Innovation Office (TIO) in the Office of Solid Waste
and Emergency Response in March, 1990. The mission assigned TIO was
to foster greater use of innovative technologies.
In October of that same year, TIO, in conjunction with the National Ad-
visory Council on Environmental Policy and Technology (NACEPT), con-
vened a workshop for representatives of consulting engineering firms, pro-
fessional societies, research organizations, and state agencies involved in
2 . The classifications were based upon information provided by process developers
or suppliers and independent sources, such as the US Environmental Protection
Agency. See Appendix A for a list of vendor contacts.
1.2
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Chapter 1
remediation. The workshop focused on defining the barriers that were im-
peding the application of innovative technologies in site remediation
projects. One of the major impediments identified was the lack of reliable
data on the performance, design parameters, and costs of innovative pro-
cesses.
The need for reliable information led TIO to approach the American
Academy of Environmental Engineers®. The Academy is a long-standing,
multidisciplinary environmental engineering professional society with
wide-ranging affiliations with the remediation and waste treatment profes-
sional communities. By June 1991, an agreement in principle (later formal-
ized as a Cooperative Agreement) was reached. The Academy would man-
age a project to develop monographs describing the state of available inno-
vative remediation technologies. Financial support would be provided by
the EPA, U.S. Department of Defense (DOD), U.S. Department of Energy
(DOE), and the Academy. The goal of both TIO and the Academy was to
develop monographs providing reliable data that would be broadly recog-
nized and accepted by the professional community, thereby, eliminating or,
at least, minimizing this impediment to the use of innovative technologies.
The Academy's strategy for achieving the goal was founded on a
multiorganization effort, WASTECH® (pronounced Waste Tech), which
joined in partnership the Air and Waste Management Association, the
American Institute of Chemical Engineers, the American Society of Civil
Engineers, the American Society of Mechanical Engineers, the Hazardous
Waste Action Coalition, the Society for Industrial Microbiology, and the
Water Environment Federation, together with the Academy, EPA, DOD,
and DOE. A Steering Committee composed of highly respected representa-
tives of these organizations having expertise in remediation technology
formulated the specific project objectives and process for developing the
monographs (see page iv for a listing of Steering Committee members).
By the end of 1991, the Steering Committee had organized the Project.
Preparation of the monograph began in earnest in January, 1992.
1.2.2 Process
The Steering Committee decided upon the technologies, or technological
areas, to be covered by each monograph, the monographs' general scope,
and the process for their development and appointed a task group composed
1.3
-------
Introduction
of five or more experts to write a manuscript for each monograph. The task
groups were appointed with a view to balancing the interests of the groups
principally concerned with the application of innovative site and waste
remediation technologies — industry, consulting engineers, research, aca-
deme, and government (see page iii for a listing of members of the Solvent/
Chemical Extraction Task Group).
The Steering Committee called upon the task groups to examine and
analyze all pertinent information available, within the Project's financial
and time constraints. This included, but was not limited to, the comprehen-
sive data on remediation technologies compiled by EPA, the store of infor-
mation possessed by the task groups' members, that of other experts willing
to voluntarily contribute their knowledge, and information supplied by pro-
cess vendors.
To develop broad, consensus-based monographs, the Steering Committee
prescribed a twofold peer review of the first drafts. One review was con-
ducted by the Steering Committee itself, employing panels consisting of
two members of the Committee supplemented by at least four other experts
(See Reviewers, page iii, for the panel that reviewed this monograph). Si-
multaneous with the Steering Committee's review, each of the professional
and technical organizations represented in the Project reviewed those mono-
graphs addressing technologies in which it has substantial interest and com-
petence. Aided by a Symposium sponsored by the Academy in October,
1992, persons having interest in the technologies were encouraged to par-
ticipate in the organizations' review.
Comments resulting from both reviews were considered by the Task
Group, appropriate adjustments were made, and a second draft published.
The second draft was accepted by the Steering Committee and participating
organizations. The statements of the organizations that formally reviewed
this monograph are presented under Reviewing Organizations on page v.
7.3 Purpose
The purpose of this monograph is to further the use of innovative SCE
site remediation- and waste processing technologies, that is, technologies not
commonly applied, where their use can provide better, more cost-effective
1.4
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Chapter 1
performance than conventional methods. To this end, the monograph docu-
ments the current state of a number of innovative SCE processes.
1.4 Objectives
The monograph's principal objective is to furnish guidance for experi-
enced, practicing professionals and users' project managers. The mono-
graph is intended, therefore, not to be prescriptive, but supportive. It is
intended to aid experienced professionals in applying their judgment in
deciding whether and how to apply the technologies addressed under the
particular circumstances confronted.
In addition, the monograph is intended to inform regulatory agency per-
sonnel and the public about the conditions under which the processes it
addresses are potentially applicable.
1.5 Scope
The monograph addresses innovative SCE technologies that have been
sufficiently developed so that they can be used in full-scale applications. It
addresses all aspects of the technologies for which sufficient data were
available to the Solvent/Chemical Extraction Task Group to describe and
explain the technologies and assess their effectiveness, limitations, and
potential applications. Laboratory- and pilot-scale studies were addressed,
as appropriate.
The monograph's primary focus is site remediation and waste treatment.
To the extent the information provided can also be applied to production
waste streams, it will provide the profession and users this additional ben-
efit. The monograph considers all waste matrices to which SCE can be
reasonably applied, such as soils, sludges, filter cake, and other solid media.
Application of site remediation and waste treatment technology is site
specific and involves consideration of a number of matters besides alterna-
tive technologies. Among them are the following that are addressed only to
1.5
-------
Introduction
the extent essential to understand the applications and limitations of the
technologies described:
• site investigations and assessments;
• planning, management, specifications, and procurement;
• regulatory requirements; and
• community acceptance of the technology.
1.6 Limitations
The information presented in this monograph has been prepared in accor-
dance with generally recognized engineering principles and practices and is
for general information only. This information should not be used without
first securing competent advice with respect to its suitability for any general
or specific application.
Readers are cautioned that the information presented is that which was
generally available during the period when the monograph was prepared.
Development of innovative site remediation and waste treatment technolo-
gies is ongoing. Accordingly, postpublication information may amplify,
alter, or render obsolete the information about the processes addressed.
Compared to many of the other classes of treatment technologies for which
monographs are being produced, solvent extraction is a young technology,
with fewer vendors that have carried their processes to full scale applica-
tion. As a consequence, the reader will se a marked variation in the amount
of information presented on different technologies. This variability in the
quantity of information presented here on different technologies only re-
flects the extent to which information has been produced and was available
to the authors; it is not intended to indicate a preference for one technology
over another.
This monograph is not intended to be and should not be construed as a
standard of any of the organizations associated with the WASTECH®
Project; nor does reference in this publication to any specific melhod, prod-
uct, process, or service constitute or imply an endorsement, recommenda-
tion, or warranty thereof.
1.6
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Chapter 1
7.7 Organization
This monograph and others in the series are organized under a uniform
outline intended to facilitate cross reference among them and comparison of
the technologies they address. Chapter 2.0, Process Summary, provides an
overview of all material presented. Chapter 3.0, Process Identification, pro-
vides comprehensive information on the processes addressed. Each process
is fully analyzed in turn. The analysis includes a description of the process
(what it does and how it does it), its scientific basis, status of development,
environmental effects, pre- and posttreatment requirements, health and
safety considerations, design data, operational considerations, and compara-
tive cost data to the extent available. Also addressed are process unique
planning and management requirements and process variations. Case stud-
ies of three of the processes are set forth in Appendices C, D, and E.
Chapter 4.0, Potential Applications, Chapter 5.0, Process Evaluation, and
Chapter 6.0, Limitations, provide a synthesis of available information and
informed judgments on the processes. Each of these chapters addresses the
processes in the same order as they are described in Chapter 3.0. Chapter
7.0, Technology Prognosis, identifies indications of the likely expanded
applications of SCE.
1.7
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Chapter 2
2
PROCESS SUMMARY
i
2. / Identification of Processes
Solvent/chemical extraction (SCE) technologies, based on well-estab-
lished scientific principles, employ a broad range of solvents to separate
contaminants from soils, sludges, sediments, and wastewater. The follow-
ing are the full-scale commercial and/or field-tested SCE processes evalu-
ated in this monograph:
• Basic Extractive Sludge Treatment (B.E.S.T.) Process;
• CF Systems;
• Carver-Greenfield Process;
• Extraksol Process;
• Low Energy Extraction Process (LEEP®)
• NuKEM Development (NKD) Process; and
• Soil Restoration Unit (S.R.U.).
The following are the emerging processes demonstrated at the bench
scale that are briefly addressed in Appendix B:
• Chemical Waste Management Adiabatic Process for the Extrac-
tion of Sludges (APES);
• Phoenix Milj0 Contex Process;
• Henkel Liquid Ion Exchange (LIX) Process;
1 . This chapter is a summary of Chapters 3.0 through 7.0. Sources are cited, where
appropriate, in those chapters.
2.1
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Process Summary
• Davy R & D Resin-in-Pulp/Carbon-in-Pulp (RIP/CIP) Process;
and
• Martin Marietta Soilex Process.
The following technologies were identified but insufficient data were
available to evaluate these technologies:
• Environment Canada's Soil Treatment Process;
• Extrapure Process by EM&C; and
• Solvent Extraction for Dredged Sludges by SRE, Inc.
2.2 Scientific Basis
Solvent/chemical extraction effects the preferential separation of one or
more constituents from one phase into a second phase. In classical chemi-
cal engineering terms, SCE is the term applied to the transfer that occurs
between two liquid phases, or between a solid and a liquid phase.
In a conventional liquid-liquid contacting system, the best separation of
solute removal that can be effected is determined by the relative solubilities
of the solute in the two liquid phases. The ratio of the solute concentrations
in the two phases at equilibrium is the equilibrium distribution coefficient.
In the very poorly or partially miscible liquid-liquid cases, contaminant
transfer is a function of relative solubilities and the equilibrium distribution
coefficient.
When a substrate is transferred from a solid to the liquid phase, the ac-
tion is called leaching. Solvent/chemical extraction is the controlled leach-
ing of contaminants from soils, sediments, and solid wastes through use of
organic solvents or nonaqueous liquids.
Solvent/chemical extraction processes used for soil/sediment cleanup
typically employ a solvent which extracts both water and organics into the
liquid phase. Subsequent steps involve first separating the liquid phase
from the solids, then separating the water and organic phase, and finally,
separating the contaminants from the solvent. As such, the extraction of the
contaminant from a solid phase involves only the equilibrium of the con-
taminant with the solvent.
2.2
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Chapter 2
2.3 Process Description
2.3.1 Basic Extractive Sludge Treatment Process
The B.E.S.T. Process, developed by the Resources Conservation Com-
pany (RCC), uses triethylamine (TEA) as the organic solvent. Below 18°C
(64°F), TEA is miscible with water and is used in dewatering solids and
partially removing organic contaminants. The remaining organic contami-
nants are removed by TEA heated to 55° to 80°C (130° to 176T), a tem-
perature range in which TEA is liquid and slightly immiscible with water
resulting in two liquid phases.
The process is carried out in a washer/dryer unit consisting of a steam-
jacketed vessel with a horizontal mixer shaft. Mixing time varies from 5 to
15 minutes per extraction.
RCC has constructed a skid-mounted, 44-kg/day (100 Ib/day) pilot plant
and a nominal 91-tonne/day (100 ton/day) full-scale, transportable system.
The full-scale system was demonstrated at one site, and achieved a maxi-
mum throughput of 64 tonne/day (72 ton/day). Throughput is expected to
vary with the composition of the feed material. The need for high-removal
efficiencies may necessitate the use of multiple extraction stages, further
reducing rated throughput.
Solids may have to be crushed and screened to meet particle size require-
ments (<2.5 cm (1 in.) in diameter). While the pilot plant can treat
pumpable and non-pumpable solids, the full-scale system treats only
pumpable waste, such as oily sludges. A portable full-scale system yet to
be constructed will be capable of handling wet or dry solids. To maintain
TEA in a nonionized state, the pH of the extraction mixture must be be-
tween 10.5 and 11.
Solids discharged from the B.E.S.T. Process are dry and oil-free, al-
though some solvent and/or organic contaminants may remain. Solids
meeting cleanup criteria may be returned to the land. The water fraction
may contain low concentrations of organic contaminants and/or residual
solvent, but may be acceptable for discharge to a publicly-owned treatment
works (POTW) without further treatment. Alternatively, when required, the
wastewater may be treated by liquid phase carbon adsorption.
2.3
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Process Summary
The organic contaminants are concentrated in the oil raffmate or fraction
and are typically recovered by distillation for recycling or treatment. De-
pending on which contaminants are present, treatment options may include
incineration, chemical dehalogenation, or recycling.
Triethylamine is a highly flammable solvent and, therefore, must be
transferred with nonsparking equipment. Restricted-access zones are re-
quired around the extraction plant. During full-scale operations previously
discussed, TEA leaks caused severe odor problems.
2.3.2 CF Systems
In the CF Systems Process, liquefied gases and supercritical fluids are
used as extraction solvents to separate organic species from wastewater,
sludge, and/or contaminated soil. Liquefied carbon dioxide is generally
used for aqueous solutions. Propane, or a mixture of propane/butane, is
often used for sediments, sludges, and soils.
In a typical operation employing liquefied propane, contaminated sedi-
ments are fed top-down into a high-pressure contactor. Compressed pro-
pane at 20°C (68°F) passes upward, counterflow to the solids, and dissolves
organic matter from the feed. The clean sediment is removed from the
contactor and the propane, which contains the organic contaminants, is
passed to a separator. The propane is vaporized, recompressed, and re-
cycled to the contactor. Contaminants and natural organic matter are re-
moved from the separation vessel and disposed or reused. The same
concept applies in the use of supercritical carbon dioxide or liquefied light
hydrocarbon gas mixtures.
Bench-scale process units are used to size pilot- and full-scale facilities.
These units employ a single-contact stage that is applied repetitively to
estimate the number of contact stages necessary to attain the desired extrac-
tion efficiency. In bench-scale studies conducted with supercritical carbon
dioxide, CF Systems (CFS) reported extraction efficiencies ranging from
95% to 100%.
On a pilot scale, CFS demonstrated a trailer-mounted unit for treating
soils, sludges, and semisolids with liquefied propane and a propane/butane
mixture. This portable unit, the Pit Cleanup Unit (PCU), utilizes two stages
of countercurrent extraction with solid-liquid separation between extractors.
The PCU has been used to treat sediments contaminated with polychlori-
2.4
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Chapter 2
nated biphenyls (PCBs), soils and sludges at nine refineries, petrochemical
plants, and treatment, storage, and disposal (TSD) facilities. Data from
pilot-scale studies in which a number of contaminated soils and wastes were
treated with liquefied light hydrocarbon gases indicate that Best Demon-
strated Available Technology (BOAT) standards were attained. Concentra-
tions for many contaminants were below detection limits after treatment.
Propane extraction has been performed on a commercial scale using a
plant having a capacity of about 23 tonne/day (25 ton/day) at a petroleum
refinery for sludge treatment. Analyses indicate that the product from com-
mercial liquefied propane extraction of refinery sludge conforms to BOAT
standards for volatile and semivolatile organic compounds. Extraction
efficiencies varied from 80% to nearly 100%.
The extent of pretreatment necessary prior to supercritical extraction is
specific to the particular site and material to be treated. To assure a rela-
tively homogeneous feed, solids removal, water addition, and mixing may
be necessary. Particles greater than 19 mm (0.75 in.) may need to be re-
moved and a suitable feed temperature must be established.
Extracted contaminants containing concentrated organic matter must be
contained, handled, stored, and transported in accordance with the Resource
Conservation and Recovery Act (RCRA) requirements. The wet sediment
product must be dewatered and the water returned for feed stream prepara-
tion, thereby reducing the need for subsequent wastewater treatment.
Propane is highly combustible and poses an explosion threat. All electri-
cal equipment must be explosion-proof; potential sources of ignition must
be eliminated where explosive gases or gas mixtures serve as the
supercritical extractant. For personnel handling treated and untreated
wastes, Occupational Safety and Health Act (OSHA) Level B or Level C
protection is recommended depending on site conditions; Level C protec-
tion is recommended, as a minimum, for extraction process operators. High
pressure operations impose a greater need for leak testing, monitoring, and
pressure vessel design detail than for conventional, domestic propane appli-
cation. Process systems must be monitored constantly to detect pressure
losses and emissions to the atmosphere. In addition, units in the recycle
train must be monitored to detect and minimize losses of contaminant to the
environment.
Before a product is discharged to the environment, it must be treated to
eliminate hazardous characteristics. The enriched contaminant stream must
2.5
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Process Summary
be completely destroyed, be stabilized for long-term storage, or its toxicity
must be substantially reduced.
2.3.3 Carver-Greenfield Process
The Carver-Greenfield Process is a drying and solvent extraction treat-
ment process that separates mixtures into solids, oil, and water, while ex-
tracting organics using a carrier oil or solvent. First, debris is separated,
and then the feed particles are ground to less than 6 mm (0.25 in.) and slur-
ried with a carrier oil or solvent to extract indigenous oils and soluble or-
ganics. The water in the slurry is evaporated in two to four multi-effect
evaporators. The vapors from the evaporation step are condensed, and the
water and carrier oil/solvent condensate are sent to an oil/water separator.
The majority of the carrier oil/solvent is separated from the feed solids by
centrifuging. The solvent is removed from the centrifuge cake by heat
stripping. The used carrier solvent is distilled to recover the carrier oil/
solvent and to separate the indigenous oils/organics. Some designs incorpo-
rate only some of the foregoing steps.
Originally developed in the 1950s, the Carver-Greenfield Process has
been used commercially to treat meat rendering wastes and nonhazardous
municipal and industrial wastes. Other commercial-scale applications in-
clude treatment of petrochemical activated sludge, biosludge and wool
scouring waste, dye wastes, alum sludge, digested and undigested municipal
wastewater sludges, and oily industrial sludge. In recent years, tests have
been conducted to determine whether the process was suitable for treating
soils and sludges contaminated with organic compounds.
Over 85 commercial-scale units have been licensed worldwide. For
those employed to treat chemical waste and sudges, feed solids generally
range from 2% to 20%, and treatment capacity ranges from 0.3 to 382 dry
tonne/day (0.33 to 420 dry ton/day). A pilot-scale unit, employed in recent
treatability tests of organic contaminated soils and sludges, has a capacity of
45kg/hr(1001b/hr).
The process requires 480-volt, three-phase electric power. For treating a
waste consisting of 52% solids, 17% indigenous oil, and 31% water (by
weight), US EPA estimated that 1.7 billion Joule would be used per tonne
of waste (1.47 MM Btu/ton). Nitrogen consumption (for deoiling) was
estimated to be 45.9 standard mVhr (1,620 standard ftVhr).
2.6
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Chapter 2
Several residues result, each requiring further treatment or disposal. The
concentrated indigenous oil and organics may be burned or refined and
reused. Although water produced by the process is substantially free of
solids and oils, it usually requires further treatment. Generally, clean, dry
solids remaining after treatment may be used for backfill or sent to a land-
fill. If inorganic compounds such as metals remain, the waste may need
further treatment. If the waste feed is a listed waste, the treated solids must
be delisted prior to disposal.
Potential environmental impacts include the effects of air emissions, dust
releases, and hazards in transporting materials. The primary environmental
impacts occur during removal of recovered indigenous oil and contaminated
solvent from the site. The closed configuration of the process reduces the
potential for air emissions. To mitigate fugitive dust emissions, the final
product may have to be treated with additives.
2.3.4 Extraksol Process
The Extraksol Process is a transportable system that uses proprietary
solvents, individually or blended together, for batch extraction of contami-
nated soils. Extraction of organic contaminants is conducted in three
phases: washing, drying, and solvent regeneration.
The extraction vessel is a mix tank without an internal agitator. The
developer claims that absence of an internal mixing system enables the
processing of large, nonporous solids, up to 0.6 m (2 ft) in diameter. Porous
solids must be no larger than 5.1 cm (2 in.). Some waste streams may need
to be dewatered prior to treatment. Agitation will break down porous pro-
cess solids during the initial extraction with hydrophilic solvents. After
each extraction, the vessel's rotation is stopped, and the solids are allowed
to settle. The contaminated solvent is decanted and pumped to a still for
solvent recovery. The number of wash cycles and the wash cycle time may
be varied.
The solvent is drained from the solids, which are then heated by intro-
ducing hot nitrogen gas and steam into the extractor. The heated gas strips
the solvent from the solids as the extraction vessel is rotated. After the gas
is removed by vacuum, it is discharged to a condenser. The contaminated
solvent is pumped to a distillation unit where low boiling point components
are volatilized, condensed, and collected for reuse as clean solvent. The
2.7
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Process Summary
remaining liquid components flow to a settling compartment. Decant from
this vessel is discharged as wastewater, which may require additional treat-
ment. Still bottoms contain the concentrated organic fraction which re-
quires further treatment, such as incineration or dehalogenation, depending
on its chemical makeup.
Bench-scale treatability tests should be conducted to determine whether
the Extraksol Process is applicable to a specific waste stream. The bench-
scale tests are conducted in a 0.23-m3 (2.5 ft3) rotary mixer that simulates
the washing cycle.
The Sanivan Group has constructed two transportable full-scale sys-
tems—one with a capacity of 0.9 tonne/hr (1 ton/hr) and another with a
capacity of 5.5 to 9 tonne/hr (6.2 to 10.1 ton/hr). Although the 0.9-l.onne/hr
system requires less than 28 m2 (300 ft2), the standard restricted access zone
associated with the process significantly expands the space required.
To minimize potential air emissions, process gases are vented through an
activated carbon filter before being released to the atmosphere. Process
wastewaters may contain low concentrations of contaminants, necessitating
additional treatment prior to discharge. Chelating agents may be used with
the solvent to mobilize lead. Chelated lead would be concentrated in the
wastewater fraction and require additional treatment before disposal.
2.3.5 Low-Energy Extraction Process
In the Low-Energy Extraction Process (LEEP®), contaminants are
leached from the solid matrix through use of a hydrophilic leaching solvent
and then concentrated using either a hydrophobia stripping solvent or distil-
lation. ART International, Inc. has developed two types of plant processes.
The "LEEP-Tar-plant" is targeted for coal tars and related compounds,
while the "LEEP-PCB-plant" is intended to treat PCBs and related com-
pounds. The two plants have similar mechanical configurations, but differ
in solvent usage and recovery.
Bench-scale studies have been conducted, and a pilot plant with a nomi-
nal throughput of 91 kg/hr, (200 Ib/hr) was completed in February 1992.
ART International, Inc. has conducted additional bench- and pilot-scale
tests since then to quantify operational parameters, and is in the process of
developing design criteria for a commercial-size LEEP-Tar-plant. The
developer anticipates a plant to be commercially operational by early 1996.
2.8
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Chapter 2
The commercial-size plants are designed to be closed loop systems ca-
pable of handling particle sizes up to 203 mm (8 in.) in diameter. If feed
materials contain free water (i.e., moisture content exceeding 50 to 70%), it
is more economical to pretreat the materials to separate the liquid and solid
matrices. For example, typical pretreatment of high moisture content mate-
rials such as sediments includes centrifugation or filtration. In the full-size
plant, solids will be fed through a grizzly/vibrating screen which rejects
oversized (>203 mm(8 in.)) material, and pieces of metal will be removed.
The solids will then be crushed to 13 to 25 mm (0.5 to 1 in.) in size and fed
to the leaching operation. The currently available pilot-scale plant is lim-
ited to treating particles less than 6 mm (0.25 in.) in size. However, larger
materials can be crushed for pilot-scale testing.
Leaching is performed at atmospheric pressure in a continuous solid/
liquid countercurrent contactor. The leaching solvent in the PCB-plant is
acetone, and in the Tar-plant the leaching occurs with acetone and a propri-
etary hydrophobic solvent. The contaminants are separated from the
leachates and concentrated either by liquid-liquid extraction using kerosene
(PCB-plant) or by distillation (Tar-plant). The kerosene with the contami-
nants is collected for off-site disposal, and the refined tar from the distilla-
tion is collected for potential commercial use.
Residual solvents associated with the leached soil are removed in a con-
tinuous dryer and are internally recycled. Any water which is leached from
the contaminated solids is separated from the acetone by distillation and
treated by carbon adsorption. The soil and water are then recombined in the
final process step and the moist soil is discharged.
2.3.6 NuKEM Development Process
NuKEM Development (NKD) is developing two waste treatment pro-
cesses employing solvent extraction. One process, using mixer/settlers, is
targeted primarily for remediation of contaminated soil. The second pro-
cess uses a continuous extraction column and is targeted for treating waste-
waters and sludges from petroleum refineries.
Contaminated soil from the excavation is screened and reduced in size to
<5 cm (2 in.) before it is fed into a mixer, where it is combined with a pro-
prietary solvent and a proprietary chemical reagent. The slurried soil leav-
ing the mixer is then fed to a countercurrent extraction system in which the
2.9
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Process Summary
organic contaminants are progressively removed as they pass through the
extraction stages. Three to five stages of extraction are usually adequate to
meet contaminant target levels.
The treated soil is fed to a solvent dryer to recover the solvent. The con-
taminated solvent (extract) is withdrawn from the first mixer/settler and is
processed in a distillation system in which the contaminants are separated
from the solvent. Personnel exposure to the waste and refinery-derived
solvent, which is flammable, should be minimized.
The soil remediation process produces clean soil and two by-product
streams — one consists of debris initially removed from the soil, and the
other is the concentrated organic waste. It is possible that very light organic
compounds may be present and build up in the solvent stream, which is
recycled. To prevent contamination of nearby aquifers, the solvent must be
thoroughly stripped from the treated soil before it is returned to the environ-
ment. Solvent losses to the atmosphere should not be significant.
A variation of this process is being developed to treat refinery waste
streams. No dewatering is required prior to treatment. The extraction is
carried out in a multistage column extractor. Solids and water flow down
the column, while solvent flows from the bottom to the top, extracting oil
from the refinery waste as it rises. The oil-laden solvent exits the top of the
column and is fed to a fractional distillation column for recovery of the
solvent. Oil-free solids and water exit the bottom of the column and are
pumped to a solvent stripper. The resulting slurry is pumped to a filter.
The filter cake is stabilized, if necessary, and sent to a landfill.
Pilot-scale studies are underway for the soil decontamination and refin-
ery waste processes. The refinery waste pilot plant had a throughput rate of
320 to 640 L/day (2 to 4 bbl/day), but was operated at higher rates from
time to time. From the results of the studies, NKD has been able to make
projections about key features of a plant intended to treat oily wastes of a 16
MM L/day (100,000 bbl/day) oil refinery. A refinery of this size will gen-
erate approximately 10,000 tonne/yr (11,000 ton/yr) of oily wastes.
2.3.7 Soil Restoration Unit
The Soil Restoration Unit (S.R.U.) uses the same three process steps as
the Extraksol Process: washing, drying, and solvent regeneration. In this
process, however, unlike batch processes, the solids are conveyed through a
2.10
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Chapter 2
specially designed extraction system where solids are mixed with
solvent(s). The S.R.U. Process consists of eight unit operations. The spe-
cific solvent(s) to be used and the time required for extraction of wastes is
determined during bench-scale treatability tests. The process can be fine-
tuned based on results in actual operation.
The system can accommodate solids up to 7.6 cm (3 in.) in diameter,
therefore, solids may have to be screened and crushed. Waste streams with
high concentrations of contaminants may be premixed with the selected
solvent to reduce overall time for extraction.
As solvent mixes with the solids, organic substances are removed. The
contaminated solvents are continuously flushed with fresh solvent, causing
solute concentrations in the solids to equilibrate with solute concentrations
in the liquid. Since the fresh solvent contains no solute, removal is limited
by diffusion or desorption of the contaminants from the solid particles.
Chelating agents may be used with the solvent during the wash cycles to
mobilize specific inorganic contaminants, such as metals. In the solids
drying unit, residual solvent is removed and a clean, dry product results.
Terra-Kleen Corporation constructed a self-contained mobile S.R.U.
capable of treating up to 1.8 tonne/hr (2 ton/hr) of contaminated solids. The
mobile unit is contained in two trailers and occupies approximately 93 m2
(1,000 ft2), not including space for support equipment. A full-scale system
has been constructed to treat approximately 2,700 tonne (3,000 ton) of soils
contaminated with PCBs and chlorobenzenes at a Superfund site.
High moisture content solids can reduce the effectiveness of the hydro-
philic solvents and increase energy costs for the distillation step. Flam-
mable solvents are employed; National Fire Protection Association (NFPA)
standards are applicable.
2.4 Potential Applications
The following section presents summaries of potential applications for
the various SCE processes. Potential applications are based on data sup-
plied by the process vendors or from US EPA SITE reports.
2.11
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Process Summary
2.4.1 Basic Extractive Sludge Treatment Process
Numerous B.E.S.T. Process bench-scale treatability tests have been per-
formed on soils, sludges, and sediments contaminated with PCBs,
polyaromatic hydrocarbons (PAHs), pesticides, and other semivolatile and
volatile organic contaminants. Highest removal efficiencies were achieved
with solids that had high initial organic contaminant concentrations, but
many of the treated solids still contained a significant amount of the con-
taminant. The treatability tests, in almost all cases, demonstrated the pro-
cess' ability to meet cleanup goals. The B.E.S.T. Process may also be used
to treat sludges from petroleum refineries and petrochemical operations.
2.4.2 CF Systems
Liquefied carbon dioxide is generally used for aqueous solutions, such as
process water and wastewater; light hydrocarbons are recommended for
sludges, sediments, and soils. Supercritical technology can be applied to a
large variety of organic contaminants. The developer has described a num-
ber of possible applications in solid and semisolid waste treatment, waste-
water treatment, and pollution prevention.
2.4.3 Carver-Greenfield Process
The Carver-Greenfield Process can be used to remove oil-soluble organ-
ics from soils, sludges, and other wastes. It can also be used to dry aqueous
mixtures and to treat wastes contaminated with organics, especially wastes
with high water content.
In some designs, commercial-scale units incorporate parts of the Carver-
Greenfield Process for unique applications. In one design, for example,
refinery sludge was dewatered with the Carver-Greenfield Process prior to
coking.
2.4.4 Extraksol Process
The Extraksol Process can be used to treat soils, sludges, and sediments
contaminated with volatile organic contaminants (VOCs), semivolatile or-
ganic contaminants (SVOCs), oils, and greases. The number of wash cycles
and their periods may be varied in order to remove specific contaminants
from solids. Considerable variability has been observed with respect to
2.12
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Chapter 2
removal efficiencies for oil and greases, as well as for specific contami-
nants. Therefore, treatability testing is encouraged prior to selecting this
technology for site remediation.
2.4.5 Low-Energy Extraction Process
The LEEP® can be used to remove coal tar and PCBs and related com-
pounds, such as creosote, petroleum hydrocarbons, PAHs, pesticides, wood-
preserving chlorophenol compounds, and pesticides from contaminated
soils, sludges, and sediments. The LEEP technology has been used to treat
river and harbor sediments, various topsoils, clay subsoil, and foundry sand.
2.4.6 NuKEM Development Process
Data have been published only on the removal of PCBs from soils and
sludges, but it is expected that the NKD Process will be effective in remov-
ing a wide range of volatile organics, semivolatile organics, pesticides and
their intermediates, petroleum hydrocarbons, and other organics. The petro-
leum refinery sludge treatment version of the process has been shown to be
effective in treating sludges from American Petroleum Institute (API) sepa-
rator, dissolved air flotation, and slop oil sludges.
2.4.7 Soil Restoration Unit
A pilot-scale system was effectively used to treat PCB-contaminated
sandblasting sand at one site. Another test, conducted on sandy loam con-
taminated with PCBs, resulted in substantial removal of the contaminants,
although according to the developer, the uninsulated system suffered con-
siderable reduction in extraction efficiencies. Soils contaminated with die-
sel fuel were also treated by this process.
2.5 Process Evaluation
2.5.1 Levels of Contaminant Removal
The seven processes studied have been shown to be effective in remov-
ing a wide range of organic contaminants from a number of different feed
2.13
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Process Summary
materials. Contaminant concentration factors as high as 10,000:1 have been
measured, this implies that these processes can provide a significant reduc-
tion in the volume of contaminants requiring further treatment.
Removal efficiencies and levels of reduction vary among the processes
depending on the nature of the process, number of extraction stages, type
and concentration of contaminants present, and the nature of the medium to
be treated. Efficiencies in removing all organic contaminants above 90%
are often reported. Residual levels below 1 ppm are also reported, but are
highly dependant on the matrix and contaminant type and concentrations.
In addition, a number (6 to 8) of extraction stages may be required to effect
those results.
2.5.2 Status of Development
All seven processes have undergone extensive testing at the bench- and
pilot-scale level, and five processes have full-sized commercial-scale sys-
tems. Three systems (CF Systems, B.E.S.T., and Carver-Greenfield) have
been demonstrated under US EPA Superfund Innovative Technology
Evaluation (SITE) demonstration programs and are fully documented. Re-
sults of test programs and evaluations have been mixed. In a number of
cases, the systems have met or exceeded test objectives, while in other cases
they have not. Therefore, treatability testing is required for most applica-
tions so that site-specific design parameters can be determined. Based on
results of treatability testing or similar applications, suppliers are offering
their systems to cover a wide variety of applications.
2.5.3 Secondary Environmental Impacts
As a separation process, SCE does not destroy organic contaminants but
produces a concentrated contaminant fraction, a treated solids fraction, and
a wastewater stream. The concentrated contaminant fraction is likely to be
a hazardous waste and, as such, is subject to hazardous waste regulations.
Incineration or another means is employed to destroy this fraction.. The
treated solids fraction and wastewater may contain residues of the: organic
contaminant and extraction fluid. Depending on the matrix treated, and the
cleanup requirements, further treatment and/or several extraction stages
may be required. Treatability studies can be helpful in assessing the matrix-
specific levels of residuals for the various SCE processes and the potential
requirement, if any, for further treatment.
2.14
-------
Chapter 2
2.5.4 Costs
Estimates of unit costs of the systems evaluated range from $105 to
$770/tonne ($95 to $700/ton) see table 5.1 on page 5.3. Costs depend on
the type of contaminant being treated and its concentration and the type of
feed material. Treatability studies and site-specific cost evaluations are
required to prepare meaningful cost estimates. Reported costs appear to be
competitive with alternative remedial technologies.
The US EPA has published detailed cost estimates for the CF Systems
Process, the Carver-Greenfield Process, and the B.E.S.T. Process.
2.6 Limitations
2.6.1 Site/Matrix Considerations
Solvent/chemical extraction processes are not normally effective in re-
moving inorganic contaminants, such as heavy metals. Although highly
effective in removing PCBs and PAHs, they may not be effective in remov-
ing hydrophilic and high molecular weight organic compounds. High con-
centrations of indigenous organic compounds in the feed can reduce
extraction efficiency and processing rates.
2.6.2 Residue Treatment
Solvent/chemical extraction produces three residue streams — treated
solids fraction, concentrated contaminant fraction, and wastewater. The
cleaned solids fraction may contain residual contaminants and extraction
fluid, as may the wastewater stream, along with soluble heavy metals. The
concentrated contaminants fraction may often require additional treatment
to assure destruction of toxic organic compounds or to prepare the fraction
to be recycled.
2.15
-------
Process Summary
2.6.3 Process Risks
Organic extraction fluids present fire hazards. Some extraction fluids are
toxic organic compounds, subject to hazardous waste regulations for stor-
age, use, transportation, and disposal.
2.6.4 Reliability
Most data reported for SCE technologies were generated by bench-scale,
pilot-scale, or demonstration plants. Little long-term data on commercial
plants are available for use in evaluating reliability. More commercial ap-
plications treating run-of-site feed are needed to demonstrate the feasibility
of SCE in handling variations in feed properties. Until such data become
available, extensive site-specific treatability testing is warranted when ap-
plying these technologies.
2.7 Technology Prognosis
The separation and concentration technique of SCE has been success-
fully applied in a wide variety of industries, including food processing,
Pharmaceuticals, fine chemicals, and mining and minerals processing.
Many of the benefits of SCE accruing in these industries will apply in the
treatment of soils, sludges, sediments, and wastewater. As additional com-
mitted systems are brought on line, process uncertainties will be reduced
and treatment costs should decrease. As additional process concepts are
developed, SCE technology will be applied more widely, leading to reduced
process costs.
2.16
-------
Chapter 3
3
PROCESS IDENTIFICATION AND
DESCRIPTION
3. / Identification of Processes
Identification of potential technologies for evaluation in this monograph
was based on information gathered from a wide variety of published and
unpublished sources (US EPA 1987; 1990c; 1992c, d, e) as well as through
personal contacts. The quantity and quality of available information for
each technology vary greatly. Some potential technologies identified have
undergone extensive testing at bench-, pilot-, and demonstration-scale lev-
els and are ready for commercial application. Others are emerging tech-
nologies requiring additional development and, for some, development has
been discontinued.
A number of solvent/chemical extraction (SCE) processes identified are
undergoing testing and/or have been evaluated in the United States Environ-
mental Protection Agency's (US EPA) Superfund Innovative Technology
Evaluation (SITE) program. Three technologies have been evaluated under
the SITE Demonstration program and test reports published. These are:
1. Resource Conservation Corporation, Basic Extractive Sludge
Treatment (B.E.S.T.) Process (US EPA 1988);
2. CF Systems, Organic Extraction Unit (US EPA 1990a); and
3. Dehydro-Tech's Carver-Greenfield Process (US EPA 1992a).
These and other processes have been shown to be effective in separating
and concentrating organic contaminants such as polychlorinated biphenyls
(PCBs), pentachlorophenol (PCP), pesticides, volatile organic compounds
(VOCs), halogenated solvents, and petroleum wastes. Generally, SCE is
3.1
-------
Process Identification and Description
not used in the treatment of soils contaminated with inorganic compounds,
although the processes are used extensively in the nonferrous minerals pro-
cessing industry to separate and recover metals such as copper, nickel, ura-
nium, and zinc. SCE processes employ several distinct process concepts
and a wide range of solvents to separate contaminants from soils, sludges,
sediments, and wastewaters. The processes are based on well-established
scientific principles (see Section 3.2, below).
The following SCE processes were selected for full evaluation:
• B.E.S.T. Process;
• CF Systems;
• Carver-Greenfield Process;
• Extraksol Process;
• Low Energy Extraction Process (LEEP®);
• NuKEM Development (NKD) Process; and
• Soil Restoration Unit (S.R.U.).
Five of the processes employ solvents at standard pressure and tempera-
ture. One process, CF Systems, employs gaseous solvents at or near the
critical pressure and temperature and another, B.E.S.T., employs critical
solution temperature solvents. See table 3.1 (on page 3.3) for a summary of
design information concerning each process.
The following are the emerging process technologies demonstrated at the
bench scale that are briefly addressed in Appendix B:
• Chemical Waste Management Adiabatic Process for the Extrac-
tion of Sludges (APES);
• Phoenix Milj0 Contex Process;
• Henkel Liquid Ion Exchange (LIX) Process;
• Davy R & D Resin-in-Pulp/Carbon-in-Pulp (RIP/C1P) Process;
and
• Martin Marietta Soilex Process.
Three additional processes were identified in the literature search for
possible inclusion in this monograph. However, due to lack of available
process data, lack of response from the process vendor, and/or indication
3.2
-------
Chapter 3
Table 3.1
Design Information
Process
B.E.S.T.
CF Systems
Carver -
Greenfield
Extraksol
LEEP®
NKD
S.R.U.
Solvent(s)
Tnethylamine
Propane/butane
carbon dioxide
Food-grade
isoparaffinic
oil(Isopar-L), Iso -
Octanol
Proprietary
Acetone, others
Proprietary
Proprietary
Proprietary
Extractor(s)
Column or batch
Column
Evaporation and
solvent extraction
stages
Batch
Multistage
countercurrent
continuous
Mixer/settler or
column
Countercurrent
continuous
Solvent
Recovery
Evaporator
and steam
stripper
Differential
pressure
Heating,
distillation,
and steam
stripping
Distillation
Liquid -
liquid exchange
dryer, and
distillation
Distillation
Distillation
Preferred Media
Soils, sludges, and
sediments
Slurried solids
High water content
wastes
Soils, sludges, and
sediments< 30%
moisture< 40% clay
Soils, sludges. and
sediments
Soils, sludges, and oily
wastewater
Soils, sludges, and
sediments< 20%
moisture low clay
that process development efforts had ceased, they were not included. These
processes are:
• Environmental Canada Soil Treatment Process;
• Extrapure Process by EM&C; and
• Solvent Extract for Dredged Sludges by SRE, Inc.
3.2 Scientific Basis
Solvent/chemical extraction effects the preferential separation of one or
more constituents from one phase into a second phase. SCE is differenti-
ated form soil washing by the use of concentrated non-aqueous reagents. In
theory, SCE can achieve higher removal efficiencies and increased contami-
nant concentration as compared to soil washing, because both chemical and
physical processes are employed.
3.3
-------
Process Identification and Description
In a conventional liquid-liquid contacting system, the solution to be
treated is called the feed, the material to be extracted is called the solute,
and the liquid selected to separate the solute is called the solvent. The sol-
vent-rich, solute-laden product is called the extract, and the residual of the
feed stream (from which solute has been removed), the raffinate. The sol-
ute concentrations in two contacting liquid phases, corresponding to equal
chemical or thermodynamic potentials, define the equilibrium state;. The
ratio of these concentrations is the "equilibrium distribution coefficient."
This is a measure of the best separation or solute removal that can be ef-
fected.
In classical chemical engineering terms, SCE is the term applied to the
transfer that occurs between two liquid phases. The two liquid phases can
be immiscible or partially miscible. Maximum separation of contaminants
is effected under the following conditions:
• the substance to be transferred between the source and the sol-
vent phases, the "solute,'" is much more soluble in the solvent
phase;
• the solvent phase is completely immiscible with the feed; and
• the solvent has a substantially different specific gravity from that
of the feed.
If solute transfer takes place from a solid substrate into a liquid phase,
the action is termed leaching. Common examples of leaching are the recov-
ery of a metal (solute) from metal ore (substrate) by treatment with strong
acid and loss of fertilizer from crop land by runoff and percolation of inci-
dent rainfall.
Although water is a principal leaching agent or solvent, the separation of
organic and inorganic contaminants from soil utilizing nonaqueous liquids
is also called leaching. SCE includes the controlled leaching of contami-
nants from soils, sediments, and solid wastes through use of organic sol-
vents or nonaqueous liquids.
Where liquid-liquid miscibility is very poor (i.e., < 1,000 mg/L or 0.1
wt.%) or merely partial, maximum possible transfer from a solid substrate is
a function of relative solubilities and the equilibrium distribution coeffi-
cient. Where the solute is bound to a solid substrate, solubility of the solute
in the solvent is balanced by low-energy sorptive binding, high-energy
chemisorption, or incorporation in the solid matrix. The chemical potential
3.4
-------
Chapter 3
of the substrate in the solid phase is a function of substrate-solid interac-
tions: weak van der Waals induced dipole forces versus strong hydrogen,
covalent, and electrostatic bonds. The stronger the interactive binding, the
poorer the equilibrium distribution coefficient.
A useful concept in explaining liquid-liquid or solid-liquid solvent ex-
traction processes is the "contact stage" or "equilibrium stage." Feed (the
liquid or solid substrate containing the contaminant to be removed), and
solvent are combined in a mixer or contactor and allowed to approach equi-
librium; subsequently, the mixed phases are settled in order to separate the
extract and raffinate phases. The combination of mixing and settling consti-
tutes a single contact stage. In turn, stages can be combined in process
trains. Partially-purified feed can be repeatedly brought into contact with
fresh solvent, reaching new equilibrium states at successively lower solute
concentrations. This design is referred to as cross-flow staging. Alterna-
tively, stages that approach equilibrium can be arranged in the counterflow
mode described in Section 3.3, below. The final feed-side residue (effluent)
stage approaches equilibrium with solute-lean solvent.
The capacity of a solvent to separate substrate x from a weakly or par-
tially soluble liquid or solid, its selectivity, is given by the following equa-
tion:
„ , . . (MassFraction x in E) I (MassFraction A in E)
Selectivity = —^
(MassFraction x in R) I (MassFraction A in R)
where:
A = Primary feed stream constituent
E = Solvent-rich phase
R = Residual phase (raffinate) at equilibrium
Selectivity must exceed unity; if it is unity, no separation is possible. If
A is water, as it is in oily wastewater, secondary sludge, sediment, or wet
soil, selectivity may determine whether the extraction technology is appli-
cable.
The vast majority of SCE processes employ solvents at near-ambient
pressures and temperatures during the extraction stage(s). Typical solvents
include alkanes, alcohols, ketones, or chlorinated solvents, used either sin-
gly or in combination.
3.5
-------
Process Identification and Description
Solvent extraction can occur under three processing approaches. The
most common approach employs two phases in contact at ambient (normal)
pressure and temperature, in which solute (contaminant) is exchanged be-
tween a solid or liquid substrate and a liquid solvent (at standard pressure
and temperature). High pressure and moderately-elevated temperatures can
be used to create efficient, dense, solvents or supercritical fluids from sub-
stances that are gases at moderate conditions (near-critical fluids). In some
instances, temperatures can be increased selectively to enhance solute trans-
fer to a solvent phase (critical solution temperature).
In another approach, near-critical fluid/liquefied gas processes use bu-
tane, isobutane, propane, carbon dioxide, or other gases liquefied under
pressure at or near ambient temperature during extraction. These processes
take advantage of special properties of gases when they are near their criti-
cal temperature and pressure (thermodynamic critical point). At this point,
the liquid and vapor phases of the solvent, in equilibrium, become identical,
forming a single phase. A fluid near its critical point exhibits the viscosity
and diffusivity of a gas, while also exhibiting the solvent characteristics of a
liquid. Under these conditions, the solvent can very effectively penetrate
the solid matrix and mobilize organic contaminants.
Finally, critical solution temperature SCE processes use solvents in
which solubility can be varied over the process operating temperature
range. These processes use liquid-liquid extraction at two different tem-
peratures. At the lower operating temperatures, the solvents are miscible,
while at the upper operating temperatures, the two solvents are completely
immiscible. In these processes, solvent recovery often consists of numerous
unit operations.
3.3 Process Description
Solvent/chemical extraction processes operate in either a batch or con-
tinuous mode, and all employ quite similar unit operations. See figure 3.1
for a diagram of a simplified process flow. The following are major unit
operations:
• feed preparation;
• extraction;
3.6
-------
Chapter 3
Figure 3.1
Solvent/Chemical Extraction — Simplified Process Flow
Solvent makeup
Contaminated
feed ^
Feed
preparation
>,
r
Extraction
vessel (s)
•^
Separation
t
Solvent
recovery
>,
T
Rejects
T
Decontaminated
solids
Concentrated
contaminants
T
Extracted
water
• solids and solvent separation; and
• solvent recovery.
Contaminated soils, sludges, or sediments are excavated and enter the
feed preparation system, where they may be screened, crushed, dewatered,
and/or slurried, depending on the particular SCE process being employed.
Chemical conditioning, such as pH adjustment, may be necessary to assure
successful extraction.
The prepared feed is then transferred to the extraction vessel(s) where it
is mixed with the extraction solvent(s). Extraction is carried out in either a
batch or continuous mode in one or a series of vessels. Selection of the
extraction solvent(s), the solvent-to-solids ratio, the extraction contact time,
and the number of extraction stages depends upon the specific contaminant
and nature of the feed. These parameters are typically determined during
treatability studies. Important solvent characteristics include relative solu-
bility of the solute, immiscibility with the feed, specific gravity, toxicity,
flammability, physical properties, chemical reactivity, ease of recovery for
recycle, and cost.
Feed and solvent streams can enter a continuous contact system in paral-
lel flow or counterflow configurations. In the counterflow arrangement,
3.7
-------
Process Identification and Description
relatively clean solvent contacts solute-lean raffinate, while feed contacts
solute-rich extract. This permits the approach to equilibrium by both end-
state pairs. The effluent streams in a parallel-flow configuration can also be
caused to approach equilibrium through use of multiple extraction stages.
In both cases, the solvent is selected to maximize the solute distribution
coefficient.
Following extraction, the decontaminated solids are separated from the
contaminant-loaded extraction solvent(s). This may be effected in the ex-
traction vessels or separately through gravity separation, filtration, centrifu-
gation, pressure reduction, or distillation. Residual solids will normally be
subjected to multiple washes in order to achieve cleanup goals. The sepa-
rated solids may retain some solvent, which is removed through distillation,
desorption, or an additional extraction step.
The contaminant-laden solvent, along with solvent vapors removed dur-
ing desorption or raffinate stripping of the decontaminated solids, is trans-
ferred to a solvent recovery system. Solvent recovery is effected through
distillation, steam stripping, pressure reduction, or phase separation. The
recovered solvent is typically recycled back to the beginning of the SCE
process, and the concentrated contaminants are removed for further treat-
ment. The extract containing the concentrated contaminants typically re-
quires further treatment before disposal or recovery.
3.4 Status of Development
Solvent/chemical extraction systems evaluated here have undergone
extensive testing at the bench- and pilot-scale levels, and several commer-
cial-scale systems are in operation. Table 3.2 (on page 3.9), summarizes the
status of development of these systems, which is discussed in subsequent
sections devoted to each.
3.5 Design Data
Available design data vary with process vendors. The most detailed in-
formation is proprietary. Five of the systems have been used commercially,
3.8
-------
Chapter 3
NKD Soil
Treatment
NKD
Refinery
Waste
S.R.U.
Table 3.2
Status of Development
Process
B.E.S.T
CF
Systems
Carver-
Greenfield
Extraksol
LEEP®
Quantity for
Treatabihty
Study
20 L (5 gal)
2 to 4 kg (5 to 10 Ib)
for bench scale.
2 to 4 kg (5 to 10
Ib) for bench
scale.
40 to 400 kg
(100 to 1,000 Ib)
for pilot plant.
25 L (6 gal)
3 to 4 kg (7 to 15 Ib)
Pilot
Unit
Capacity
45 kg/day
(lOOlb/day)
45 to 90
kg/day
(100 to 200
Ib/day)
45 kg/hr
(100 Ib/hr)
0 9 tonne/hr
(1 ton/hr)
90 kg/hr
(200 Ib/hr)
Commercial
Unit Capacity
90 tonne/day
(100 ton/day)
Sludge/solids-
9 to 900 tonne/day
(10 to 1 ,000 ton/day)
Wastewater.
20 to 550 Umin
(5 to 150 gal/mm)
Representative range:
4 5 to 45 tonne/day
(5 to 50 ton/day)
0.9 tonne/hr
(1 ton/hr)
9 tonne/hr
(10 ton/hr)
7 tonne/hr (7.7 ton/hr
(dry)) mobile plant
Planned goal
13 tonne/hr (14. 3 ton/hr
(dry)) stationary plant
Comments
Third generation
commercial system
designed.
Variety of commercial
scale units available.
Stated capacity of 1 8
installed commercial units
(including drying units):
0.3 to 420 dry ton/day.
A 5.5 to 9 tonne/hr (6 to 10
ton/hr) unit is constructed.
Commercial-scale unit
designed.
Bench:
30 grams (I oz)
6 to 100 kg
(15 to 250 Ib)
None
480 L/day
(126 gal/day)
None
None
1.8tonne/hr
(2 ton/hr)
Mobile unit constructed.
and two (CF Systems and Carver-Greenfield) have undergone US EPA
SITE Program evaluations. For five processes, US EPA technology profiles
have been completed, and US EPA technology evaluation reports are avail-
able for three (US EPA 1992g; 1989; 1988; 1992a). Sizing and scale-up
data are available for all of the processes. Specific design data for each
process are presented in the section devoted to that process.
3.9
-------
Process Identification and Description
3.6 Pre-and Posttreatment
The seven SCE processes addressed can treat a wide variety of materials;
but all require some feed pretreatment. Pretreatment generally consists of
physical sizing and, in some cases, chemical conditioning of materials be-
fore they are fed to the extraction vessel. See table 3.3.
Soils must be screened after excavation to remove oversized material,
which may then be rejected or crushed and treated, depending on the feed
material and the type of contamination. Some processes may require the
addition of water to a minimum level, whereas others may require solids
and liquids separation.
The products of the SCE process include decontaminated solids, a con-
centrated contaminants fraction, wastewater, and contaminated solvents.
Each of these streams may require additional treatment depending on re-
quired cleanup levels, the nature of the contaminants, and the final disposi-
tion of the stream. The decontaminated solids may contain trace amounts
of solvent, as well as the original contaminants. Under some process condi-
tions, naturally-occurring organic substances will be extracted and bacteria
Table 3.3
Summary of Pretreatment Requirements
Process Pretreatment Requirements
B.E.S.T. Screen to 6 mm (0.25 in.). pH adjustment to 10.5 to 11.
CF Systems Screen to 9 mm (0.19 in.) pH adjustment to between 6 and 10.
Viscosity adjustment to <5,000 cP. Temperature to 15'- 50'C
(60°-120°F) range.
Carver-Greenfield Treats wastes up to 99% water, but staged process may require
evaporative stages prior to extraction stages for high water content
wastes.
Screen particles to 6 mm (0.25 in )
Extraksol Screen porous material to 51 mm (2 in.).
Dewatering to <30% moisture content
LEEP® Removal of debris (>203 mm (>8 in.)).
Crush and screen to 13 to 25 mm (0.5 to 1 in.).
Free water removed by filtration or centrifugation.
NKD Soil Treatment Screen to remove debris
Reduce size and/or screen to <50 mm (2 in.) particle size.
NKD Refinery Waste Feed cannot contain >60 mesh particles.
S.R.U. Screen porous material to 7.6 cm (3 in.).
Dewater to <20% moisture content.
Solvent premix for high concentration wastes
3.10
-------
Chapter 3
will be killed. This will render the soils sterile, possibly requiring addi-
tional treatment to reestablish beneficial bacteria.
The concentrated contaminant stream will contain the organic contami-
nants, oil and grease, some naturally-occurring organic substances, and
small amounts of the extraction solvent(s). The concentration of organic
contaminants may be on the order of several hundred to ten thousand times
that in the contaminated feed. This low-volume, highly-concentrated
stream will most likely have to be destroyed by incineration, wet oxidation,
or other destructive process. In some cases, depending on the contaminants
present, it may be possible to recover this stream for recycling/reuse.
When moisture-containing feed materials are processed, a solvent and
water mixture is often generated. This mixture is normally separated
through distillation, which will produce a water stream containing low-
volatility, water-soluble contaminants, as well as small amounts of residual
solvent. The quantity and quality of water produced will vary from applica-
tion to application. Additional treatment will depend on the ultimate use of
the water. In some cases, it may be possible to discharge it directly to a
publicly owned treatment works (POTW).
Pre- and posttreatment requirements specific to each process are dis-
cussed in the section devoted to that process.
3.7 Environmental Impact
Each of the processes addressed can potentially impact air, water, and
land. Air emissions can result from process leaks and/or from purposeful
venting of gases. Vented air can be treated by carbon adsorption or other
systems. The majority of the chemical solvent extraction systems reviewed
use nitrogen blankets to minimize emissions and minimize potential explo-
sive hazards. Because some of the solvents used are proprietary, compre-
hensive information on potential air emissions problems was not available.
It is known, however, that odor problems have arisen in some tests. The
B.E.S.T. system, for example, uses triethylamine (TEA), which has a strong
fishy/ammonia odor. During full-scale operation, leaking seals caused ex-
cessive emissions, which resulted in Level B protection (OSHA) being
3.11
-------
Process Identification and Description
specified for operating personnel. This level of protection is not expected
for a commercial operation.
Residues from each process might impact both water and land. Often,
coarse fractions cannot be treated because particles are oversize. These
fractions may be crushed for either processing in solvent extraction systems
or they may be treated by other methods. Increased handling of contami-
nated materials, however, especially materials contaminated with volatile
organic compounds, may result in excessive fugitive emissions.
Solvent extraction produces water and solid fractions that may adversely
affect water and land. Water is separated from the treatment solvent in each
process. The residual wastewater will generally contain residual organic
contaminants and extraction fluid, as well as soluble heavy metals present
in the feed material. Treatment will be required before discharge to a water
course and may be required before discharge to a POTW.
Residual solids are separated from the treatment solvent once extraction
is complete. If the feed was a hazardous waste, the treated soil may require
disposal as a hazardous waste. Alternatively, after being treated, the soil
may be classified as non-hazardous.
In some instances, treated soil may exhibit higher concentrations of met-
als than the feedstock because of the effects of volume reduction. The ac-
tual leachability of the metals, however, may not increase, and therefore,
the solids may be considered clean. Even if elevated levels of inorganics
remain, the removal of organic contaminants may facilitate additional treat-
ment, such as stabilization.
If the solids are clean, they may be backfilled on site or used for other
purposes. During treatment, solids are dried. Several systems add steam or
water to the treated solids to reduce dust. Other systems discharge dry, fine,
dusty materials, which may be treated with additives to control dust. In
some instances, however, the cleaned solids fraction may contain residues
of the original organic contaminants and the extraction fluid and may re-
quire further treatment. If heavy metals are present in the raw feed mate-
rial, they may become concentrated in the cleaned solids. This residual may
be classified as a Resource Conservation and Recovery Act (RCRA) haz-
ardous waste, subject to land disposal restrictions and, therefore, require
stabilization or other treatment.
3.12
-------
Chapter 3
The final residues of concern are the solvent and the extracted organic
contaminants. In most systems, the solvent is recovered and recycled. The
concentrated contaminant fraction may be classified as a hazardous waste
and, therefore, be subject to regulation under RCRA. Such a waste stream
must be destroyed through incineration or other appropriate means. Once
treatment is completed, the solvent will generally require disposal as a haz-
ardous waste. Again, because some of the solvents are proprietary, compre-
hensive disposal issues for the solvents cannot be examined here.
Specific environmental impacts of each process are addressed in the
section devoted to that process.
3.8 Basic Extractive Sludge Treatment
Process
3.8.1 Description
Resources Conservation Company (RCC) of Bellevue, Washington,
developed the patented B.E.S.T. Process, in which the unique miscibility
properties of certain amine solvents are applied to separate sludges or oil-
contaminated solids into their oil, water, and solids fractions (Robbins
1990; Tose 1987; Weimer 1989). Triethylamine (TEA) is the organic sol-
vent used in this process. At temperatures below 18°C (64°F), TEA is fully
miscible with water, and above this temperature, only slightly miscible.
Therefore, cold TEA can be used to dewater solids, and, at the same time,
organic contaminants are partially removed. The remaining organic con-
taminants are removed by TEA heated to temperatures above 55 °C (130°F)
and below 80°C (176°F). Within this temperature range, TEA is liquid and
is not miscible with water (Weimer 1989).
In the B.E.S.T. Process (figure 3.2 on page 3.14), contaminated solids
are loaded into a washer/dryer unit, a steam-jacketed vessel with a horizon-
tal mixer shaft, to 25% of its capacity. A predetermined amount of caustic
is added to increase the final mixture pH to between 10.5 and 11. The ves-
sel is sealed and purged with nitrogen gas to remove residual oxygen and to
provide a nonexplosive environment for the washing and drying steps.
3.13
-------
Process Identification and Description
Figure 3.2
B.E.S.T. Process Schematic
Centrifuge
Screened
contaminated !Z^~
soil
Condenser
Solvent
evaporator
Concentrated
contaminants
Chiller
Chilled solvent (<6°C (<43°F)) is added to fill the vessel, resulting in a
solvent-to-soil ratio of 3:1. The extraction phase begins when the mixer
shaft motor is activated. Paddles, affixed to the shaft, sweep the inside
diameter of the vessel. This agitation mixes the solvent and solids. Mixing
time varies from 5 to 15 minutes per extraction.
At the end of each extraction step, the mixer is stopped and the solids are
allowed to settle. Since TEA has a low specific gravity (0.73 @ 20°C
(70°F)), solids, which would normally stay in suspension in water, will
settle out. The TEA, water, and oil mixture is decanted and pumped to a
centrifuge. The centrifuge separates any residual solids from the mixture
and returns the solids to the washer/dryer for additional extractions. The
concentrate is heated in an evaporator to about 77°C (170°F). At this tem-
perature, the TEA/water azeotrope will evaporate, leaving the oil phase,
which is removed from the bottom of the evaporator. The TEA/water va-
pors are condensed and flow into a decanter. Since TEA and water are
3.14
-------
Chapter 3
immiscible at temperatures above 55°C (130°F), the condensed TEA and
water separate into two distinct phases in the decanter. Water is pumped
from the decanter to a steam stripper. The steam stripper volatilizes re-
sidual TEA and discharges an aqueous stream. Gaseous TEA, discharged
from the top of the steam stripper, is condensed and collected in the de-
canter, and the condensate serves as the feed to the steam stripper. De-
canted TEA is recycled for additional extractions.
Subsequent extractions are carried out at temperatures above 55°C
(130°F). At this temperature, the solubility of organic contaminants in TEA
increases, thus increasing removal efficiencies. At the completion of the
extractions, steam is injected into the washer/dryer's jacket, and the mixing
shaft is rotated. As the temperature of the washer/dryer increases, TEA
volatilizes, thereby producing a dry solids product. Live steam may be
injected directly into the washer/dryer near the end of the drying cycle to
return moisture to the solids. This measure helps control fugitive dust when
the solids are discharged.
3.8.2 Status of Development
RCC has developed a B.E.S.T. Process treatability test, performed in the
company's laboratory. The test simulates the process steps employed by
the full-scale and pilot-plant units and is used to determine the amount of
caustic required for pH adjustment. It is also used to determine the total
number of extraction stages required to achieve cleanup goals.
For this test, chilled TEA is mixed with a measured quantity of solids.
The solids are permitted to settle, the TEA is decanted, and the solids are
centrifuged. The solids may be sampled at the completion of each extrac-
tion for analysis. Alternatively, if high removal efficiencies (>95%) must
be achieved to demonstrate effectiveness, solids sampling may be initiated
after the completion of several extractions (Robbins 1990).
RCC has constructed a 44-kg/day (100 Ib/day) B.E.S.T. pilot plant. The
skid-mounted module contains all the unit processes and is easily trans-
ported on highways. The pilot plant was used for treatability testing on
PCB-contaminated soils at spill sites in Ohio and New York (Robbins
1990). Additional SITE demonstration testing of this system has been com-
pleted (Meckes et al. 1992; US EPA 1993).
3.15
-------
Process Identification and Description
3.8.3 Design Data
As explained in Subsection 3.8.1, the B.E.S.T. Process is designed to
capitalize upon the unique properties of the organic solvent TEA. When
contaminated solids are mixed with chilled TEA, the water and organic
contaminants will be extracted. Once dewatering of the solids has been
completed, additional extractions are conducted at temperatures above 55°C
(130°F). At this temperature, the solubility of organic contaminants in TEA
increases, thereby enhancing the capacity for removal of organic wastes.
According to Tose (1987), design throughput for the full-scale B.E.S.T.
transportable system is 91 tonne/day (100 ton/day). Maximum throughput
during cleanup activities at the General Refining Site, however, was shown
to be 64 tonne/day (72 ton/day). Nominal composition of the sludge treated
at this site was 70% water, 20% solids, and 10% oil. During operalion, the
composition of the sludge ranged from 60% to 100% water, 0% to 40% oil,
and 2% to 30% solids (US EPA 1988). Throughput was found to vary with
the feed material's composition. Furthermore, the need for high contami-
nant removal efficiencies associated with contaminant levels may have
necessitated multiple extraction stages. This would also reduce rated
throughput.
The system used at the General Refining Site is designed to accept
pumpable fluids. Waste streams that are not pumpable must be modified to
accommodate the pumps feeding the extraction column.
The B.E.S.T. pilot plant uses a washer/dryer system (Robbins 1990;
Weimer 1989). This system represents RCC's current approach to the
B.E.S.T. Process. Both pumpable or nonpumpable solids may be loaded
into the washer/dryer, where all operations involving the solids take place.
This practice minimizes solids handling requirements and results in a batch-
feed operation. Since dewatering of solids can be effected by use of chilled
TEA and separation of TEA/water mixtures can be induced by increasing
the mixture temperature above 55°C (130°F), high moisture content solids,
such as sludges and sediments, may be dewatered with a low expenditure of
energy.
3.8.4 Pre- and Posttreatment
The full-scale B.E.S.T. systems can treat pumpable waste flows with a
particle size < 2.5 cm (1 in.) in diameter. The B.E.S.T. pilot plant can treat
3.16
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Chapter 3
pumpable and non pumpable solids with a particle size < 6 mm (0.25 in.).
Material classifiers, such as shredders and screens, may be required to re-
duce the waste to these particle sizes. According to RCC, future production
models will accommodate solids with a diameter < 2.5 cm (1 in.). In order
to maintain TEA in a nonionized state, the pH of the final extraction mix-
ture must be between 10.5 and 11. The amount of caustic to be added to the
extractor is determined by treatability tests (Robbins 1990; Tose 1987;
Weimer 1989).
Solids discharged from the B.E.S.T. Process are dry and oil free with a
pH in the range of the final extraction mixture. Some residual solvent and/
or organic contamination may remain. If the original waste stream con-
tained inorganic contaminants, such as metals, they will remain with the
solid fraction. Solutions containing concentrations up to 200 mg/kg TEA in
water are known to biodegrade. No available data, however, document
degradation of TEA in soils (Meckes et al. 1992). When offered for dis-
posal, concentrated TEA is considered to be a hazardous waste since it
meets the definition for ignitability in 40CFR261.21. However, it is un-
likely that residual TEA concentrations of <200 mg/kg in soils will meet the
regulatory definition of "ignitability".
Solids meeting cleanup criteria may be returned to the land for reuse.
Since beneficial organic matter may also be removed by the extraction pro-
cess, augmentation of the treated solids with organic substrate may be nec-
essary to promote degradation of residual solvent or support vegetative
growth. Depending on the extent of metal or other inorganic contamina-
tion, the solvent-extracted solids may need to be treated by some other tech-
nique, such as stabilization/solidification or soil washing (Meckes et al.
1992; US EPA 1990c).
The physical properties of the treated solids are similar to the feed mate-
rial. In many cases, they can be compacted and backfilled (after the addi-
tion of water) as is. While in other instances, they may require the addition
of stabilizing materials to achieve acceptable compaction properties.
Water produced through this process should be analyzed for the
contaminant(s) of concern and residual solvent. Low concentrations of
organic contaminants may remain with the water fraction, although, the
water may be acceptable for discharge to a POTW. Liquid phase carbon
adsorption may be used to produce an aqueous discharge free of organic
contaminants.
3.17
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Process Identification and Description
Organic contaminants are concentrated in the oil fraction. If chlorinated
hydrocarbons, such as PCBs and many pesticides, are among the contami-
nants of concern, the treatment options are incineration or chemical
dehalogenation. If chlorinated hydrocarbons are not among the contami-
nants of concern, the concentrated waste stream may be recycled.
3.8.5 Operational Considerations
The 91 tonne/day-transportable unit, excluding support equipment, occu-
pies an area of approximately 335 m2 (3,600 ft2) (US EPA 1988). Support
equipment consists of material classifiers, makeup solvent tanks, caustic
tanks, and water treatment equipment. This unit is designed to treat
pumpable solids only. Therefore, some modification of the waste stream
may be required. RCC's B.E.S.T. pilot plant uses a washer/dryer system
that will treat pumpable or nonpumpable solids.
Triethylamine, having an open cup flash point of -4°C (25°F), is a highly
flammable solvent. Transfer of solvent from storage to process tanks must
be effected with nonsparking equipment. Chapter 5 of the National Fire
Protection Association (NFPA) standard states that a restricted access zone
must extend to a 15-m (50 ft) radius around the extraction plant and a con-
trol zone must extend from the 15-m (50 ft) line to a radius of 30 m (100 ft)
from the extraction plant (NFPA 1990). Therefore, siting the system at
some locations may be difficult.
3.8.6 Environmental Impacts
Triethylamine has a strong ammonia-like odor. During full-scale opera-
tion, seals on a centrifuge developed leaks, released low concentrations of
TEA, and caused an offensive odor (US EPA 1988). Newer washer/dryer
designs do not use the same type of system for product dewatering; vapors
discharge through activated carbon filters, which mitigate the odor. Waste-
water generated via this process may contain low concentrations of organic
and inorganic contaminants and require treatment before discharge.
3.18
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Chapter 3
3.9 CFSystems
3.9.1 Description
The CF Systems Corporation (CFS) of Woburn, Massachusetts, and CF
Technologies Inc. (CFT) of Hyde Park, Massachusetts, specialize in the
development and application of supercritical fluid and liquefied gas extrac-
tion processes for chemical production and hazardous waste treatment. Liq-
uefied gases are used as extracting solvents to separate organic solutes and
sorbates from wastewater, sludge, and contaminated soil. Target contami-
nants include hydrocarbons (benzene, toluene, xylene (BTX) and constitu-
ents of gasoline), oil and grease, partially-oxidized hydrocarbons (phenol,
alcohols, fatty acids, acetone, etc.), and chlorinated species (PCBs and
dichloroethane). Carbon dioxide (CO2) is generally used for aqueous solu-
tions; propane is often selected for sediments, sludges, and soils. In select-
ing the solvent, the solubility of CO2 in water and the effects on pH and
soluble inorganic salt content must be considered. Propane is a volatile,
flammable, hydrocarbon that can constitute a fire and explosion hazard in
the event of system malfunction.
Figure 3.3 (on page 3.20) is a simplified diagram of a one-stage solvent
extraction process employing liquefied propane. Contaminated sediments
are fed top down into a high-pressure contactor. Compressed liquefied
propane at 20°C (70°F) passes upward, counter to the solids, and dissolves
organic matter. Clean sediment (raffinate) is removed from the contactor.
A solution of organic contaminants in propane is passed to a separator via a
pressure-reducing valve. Propane is vaporized, recompressed, and recycled
to the contactor as fresh solvent. Contaminants and natural organic matter
are removed from the separation vessel and recovered for disposal or reuse.
The process has seven basic operating steps. Initially, slurried sludge is
fed to a stirred-tank extractor (raw sludge may require pretreatment to
eliminate oversized material or to modify chemical characteristics, such as
pH). Propane is compressed to operating pressure, condensed, and fed to
the extraction vessel to dissolve oil in the sludge feed. A mixed stream is
taken from the contactor to a decanter, in which gravity separation of the
heavier water and solids fraction and the lighter propane and oil fraction
occurs. Water and treated solids are removed from the decanter; the solids
are dewatered and the final filter cake is removed to landfills.
3.19
-------
Process Identification and Description
Propane and oil pass to a solvent-recovery still. The distillation tower
operates at a reduced pressure. The reboiler is heated with recompressed
propane vapor. Oil, collected as still bottoms, is recycled to the refinery,
and propane is recycled as fresh solvent.
This one-step mixer/settler system is actually operated as a multiple-
stage process. The number of stages must be suitable to achieve best dem-
onstrated available technology (BOAT) standards for refinery hazardous
wastes (K048-K052) prescribed by US EPA. The number of stages re-
quired (typically 2 to 5) is dependent on the feed matrix and type and level
of contaminants present. The treated oil and solids raffinate stream from
the commercial unit is claimed to conform to BOAT standards for sixteen
specific volatile and semivolatile organic compounds.
The same concept can be applied with supercritical carbon dioxide or
liquefied light hydrocarbon gas mixtures as the solvent. These modified
processes have been evaluated at bench and pilot scales.
Figure 3.3
CF Systems Solvent Extraction Unit Process Diagram
Sediments
Extraction
vessel
Separator
Compressor
Propane
Concentrated
contaminants
Decontaminated
sediments
US EPA 1990s
3.20
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Chapter 3
3.9.2 Status of Development
Supercritical CO2 has been used by CFS in treating contaminated
groundwater and soils, wastewaters, and sludges. Removal of volatile and
semivolatile organics has been demonstrated at bench scale. Liquefied
propane has been used to extract organic contaminants from refinery slud-
ges, separator sludges, and soils. Bench operations employ a single-contact
stage that can be used repetitively to aid in estimating the number of pilot-
and full-scale contact stages necessary to attain the desired extraction effi-
ciency. Results of bench-scale studies approach classic equilibrium thermo-
dynamic measurements. In general, small-scale studies have suggested that
the use of liquefied gas in extracting organic contaminants from semisolids
is somewhat less efficient than in extracting them from aqueous wastes.
At the pilot scale, CFS has demonstrated a trailer-mounted unit, the Pit
Cleanup Unit (PCU), in treating soils, sludges, and semisolids with lique-
fied propane and a propane/butane mixture. This light hydrocarbon
supercritical extraction unit uses two stages of countercurrent extraction
with solid-liquid separation between extractors. Feed slurry is passed
through a basket filter to remove particles larger than 3 mm (0.12 in.) in
diameter. An agitator provides mixing action between contactor and de-
canter pairs. Two immiscible phases develop in Decanter 1; solids and
water settled in this unit are pumped to Extractor 2. Decanter overflow,
containing extracted organic substances, propane, butane, and fine solids, is
filtered and sent to a solvent recovery still.
In the primary demonstration of the PCU, at the New Bedford, Massa-
chusetts, Superfund Site, the Corps of Engineers dredged and drummed
sediments contaminated with concentrations of PCBs as great as 2,600 ppm
(US EPA 1990a). In addition, CFS has used the PCU to treat soils and
sludges at nine refineries, petrochemical plants, and treatment, storage, and
disposal (TSD) facilities. The PCU has also been used to treat a 1:1 mix-
ture of American Petroleum Institute (API) separator sludge and dissolved
air flotation (DAF) sludges, material from a clay pit, ditch skimmer sludge,
and tank bottoms.
The propane extraction process has been deployed to treat sludge at the
Texaco Star Enterprise petroleum refinery in Port Arthur, Texas. Treatment
plant capacity is approximately 23 tonne/day (25 ton/day). The solvent is
liquefied propane at pressures of about 2.1 MPa (300 psig) and tempera-
tures of 32° to 49°C (90° to 120°F).
3.21
-------
Process Identification and Description
3.9.3 Design Data
Analysis of commercial liquefied propane extraction of refiner)' sludge
indicates that raffinate conforms to BDAT standards for volatile and
semivolatile organic compounds. See table 3.4 for a summary of results of
testing performed on a commercial system. Extraction efficiencies for the
class of contaminants under consideration varied from 80% to approxi-
mately 100% for liquefied propane extraction using typically 1 to 5 extrac-
tion stages.
Table 3.4
CF Systems - Commercial System
Compound Concentration (ppm)
Benzene
Toluene
Total Xylene
Naphthalene
Benzo(a)pyrene
Typical Treated Solids
< Detection Limit
< Detection Limit
38
10.7
< Detection Limit
BDAT Standard
14
14
22
42
12
Pilot-scale studies of liquefied light hydrocarbon gases have been per-
formed using the PCU on a number of soils and wastes, including: (1) a
contaminated soil from the United Creosote Superfund Site, Conroe, Texas,
(2) a 1:1 mixture of API separator sludge and DAF sludge, (3) clay-pit resi-
dues (Port Arthur, Texas), and (4) ditch-skimmer sludge. Selected data
from three of the studies presented in table 3.5 (on page 3.23) reflect the
attainment of BDAT standards and concentrations below detection limits
after treatment. In pilot-scale studies of supercritical extraction of sedi-
ments contaminated with PCBs performed as part of the SITE Program at
New Bedford, Massachusetts (see Subsection 3.9.2) the solvent was a 70:30
mix of propane/butane. Three series of evaluations were conducted with
the two-stage operating systems. A series consisting of a number of se-
quential passes of sediments contaminated with PCBs in concentrations of
288 to 2,575 ppm demonstrated great variations in distribution coefficients
3.22
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Chapter 3
Table 3.5
CF Systems - Pilot Plant Data
Compound
Concentration (mg/kg)
United Creosote Soil
Treated
Feed Soil
Water (wt %)
Solids (wt %)
Oil and grease (wt %)
Benzene (ppm)
Toluene (ppm)
Naphthalene (ppm) 140 1 5
Pyrene (ppm) 360 1 1
Mixed Sludge
Feed
533
380
8.7
11.9
88.5
478
125
Treated
Soil
341
659
0012
0.13
0.5
03
Clay Pit Residue
Feed
60.5
223
17.2
9.6
16
210
Treated
Soil
1.9
<01
<01
<5.3
and solids retention. Removal efficiencies were as high as 90%; extraction
efficiencies of 60% were generally attained in the first pass of each test
series. A mass balance for PCBs was not possible. A greater mass of con-
taminant was reported for process effluents and for decontamination washes
than had apparently been fed to the system. The cause of these anomalies is
not known.
In three PCB-contaminated sediment tests, feed slurry flow varied be-
tween 2.5 and 6.5 L/min (0.6 and 1.4 gal/min). Supercritical solvent flow
varied widely outside the desired range of 3.5 to 7 kg/min (8 to 15 Ib/min);
thus, the solvent/feed ratio also fluctuated widely.
Bench-scale studies are best conducted in a single-stage, near-equilib-
rium context. With supercritical CO2, CFS reports very high thermody-
namic efficiencies; at concentrations of 0.4 to 520 ppm, extraction
efficiencies are reported to vary from 95 to 99.99%. These measurements
are equivalent to distribution coefficients as large as 10s for chloroform,
dichloroethane, and trichloroethane. The distribution coefficients for
Aroclor 1242 and phenol are approximately 20.
3.9.4 Pre- and Posttreatment
Pretreatment of wastes in supercritical extraction will be specific to the
site and materials to be handled. Experience with sediments from New
3.23
-------
Process Identification and Description
Bedford, Massachusetts, indicated a need to remove particles greater than
19 mm (0.75 in.) in order to decrease viscosity and establish a suitable feed
temperature. Feed consistency must be relatively homogeneous to provide
adequate control of flow rates. Solids removal, water addition, mixing, and
storage capacity are important pretreatment considerations. In the New
Bedford Harbor SITE demonstration test, using supercritical propane, siev-
ing and screening were important (US EPA 1990a).
Vibrating screens are widely used because of their large capacity and the
resulting high efficiency; however, wet or sticky materials tend to blind the
screen. Wet screening with sprays is probably appropriate to inhibit blind-
ing. Manual or automated high-pressure water sprays are assumed to be
adequate to treat oversized solids. Coarse solids would be disposed of with
fine-grained materials treated by CF Systems' supercritical extraction tech-
nology. Spray water should be collected and reused.
Posttreatment must be considered for two product streams generated by
the supercritical extraction process. The extract contains concentrated or-
ganic matter and treated sediments contain water and solids. Extracted
contaminants must be contained, handled, stored, and transported off site in
a manner conforming with RCRA requirements. The volume of raw sedi-
ment would be less than the volume of treated effluent. The wet product
must be dewatered, and the water must be returned for feed stream prepara-
tion to minimize wastewater treatment requirements.
Pretreatment for the CF Systems SITE demonstration at the New
Bedford site consisted of dredging, sediment storage and handling., coarse
solids separation, water addition, and temperature adjustment. Posttreat-
ment consisted of dewatering treated sediment, disposal of treated sedi-
ments, and off-site disposal of extracted organic matter.
3.9.5 Operational Considerations
Foaming in treated sediment and extracted contaminant tanks was evi-
dent throughout SITE project experiments (US EPA 1990a). The suspected
cause was propane entrainment. Foaming has two adverse effects: (1)
extracted contaminant (PCBs) persists in the foam and (2) increased volume
of the product stream leads to higher costs and likely contaminant migra-
tion. Commercial process designs will probably utilize multiple pressure
3.24
-------
Chapter 3
relief steps to decrease pressure gradually and reduce the potential for pro-
pane entrainment.
Retention of solids and oily contaminants in the New Bedford SITE sys-
tem (see Subsection 3.9.2) influenced the interpretation of test data. The
CF Systems pilot unit was operated in a recycle mode to simulate multiple
stages. This led to some cross-contamination of recycled, treated sedi-
ments. To prevent cross-contamination in operations that involve substan-
tial feed stream changes, oil and contaminant removal with an organic
solvent is recommended.
During the SITE tests, there was no acute threat to operator health and
safety. Combustible gas meters, used to monitor the test unit, did not indi-
cate any significant leakage of propane, which is highly combustible and
poses an explosion threat. High-pressure operations create a greater need
for leak testing, monitoring, and pressure vessel design detail than do con-
ventional, domestic propane applications. Background air sampling and
personnel monitoring indicated that organic vapor and PCB concentration,
if present, were at levels below detection limits. Gases vented from the unit
were passed through a carbon canister. They contained minor concentra-
tions of PCBs. The greatest threat to SITE project workers was deemed to
be dermal exposure. For personnel handling treated and untreated wastes,
Occupational Safety and Health Act (OSHA) Level B personnel protection
equipment (PPE) is recommended. Level C PPE is recommended for ex-
traction process operators. The PPE clothing should be designed for the
materials handled and the environment of the process.
All electrical equipment must be explosion proof (US EPA 1990a). Po-
tential sources of ignition must be eliminated in the process plant area when
propane, butane, or propane and butane mixtures serve as the supercritical
extractant. Spark-proof tools must be used in all instances. Solvent recov-
ery is similar to commercial refinery depropanizer operation, which has a
long history of safe, efficient use in the international petrochemical indus-
try.
If supercritical CO2 is selected as the solvent, fire and explosion hazards
are mitigated. However, CO2 may still present a health hazard in confined
areas. Leakage still represents a pathway for losses of extracted contami-
nant. Total pressure is higher than in the case of hydrocarbons, and this
requires careful consideration of high pressure design criteria. System fail-
ure at elevated pressure constitutes a source of physical hazard to plant
3.25
-------
Process Identification and Description
operators. In addition, unexpected pressure release could result in discharge
of extracted contaminants before controlled separation and disposal. Again,
OSHA Level B and Level C PPE are appropriate because of the hazardous
nature of the contaminants present in feed sediment, sludge, or soil.
3.9.6 Environmental Impacts
Process systems must be monitored continuously for pressure losses and
emissions to the atmosphere. These emissions constitute a fire and/or ex-
plosion hazard where light hydrocarbons are used and a source of process
instability where supercritical carbon dioxide is used. In both cases, or-
ganic contaminants are concentrated in the solvent, and leakage or spillage
may release a hazardous vapor or aerosol to the atmosphere. The overall
process provides means for contaminant separation, solvent recovery, and
solvent repressurization for reuse in waste contacting units. Since the goal
is to maximize contaminant concentration in the solvent stream, solvent
management is particularly critical. Units in the recycle train must be
monitored closely to detect losses of contaminant to the environment.
A hazardous waste feed may lead to a hazardous product. The product
may be wastewater requiring further treatment, relatively dry soil, or sedi-
ment. After treatment, the product must be evaluated to establish its haz-
ardous characteristics. Treatment after supercritical fluid extraction must be
designed to eliminate hazardous characteristics before a product is dis-
charged to the environment. The enriched contaminant stream must be
completely destroyed, substantially reduced in toxicity, or stabilized for
safe, long-term storage.
3.70 Carver-Greenfield Process
3.10.1 Description
The Carver-Greenfield Process is a patented drying and solvent extrac-
tion treatment process, which is commercially available from the Dehydro-
Tech Corporation (DTC). The process separates mixtures into solids, oil,
and water, while extracting organics using a carrier oil or solvent (US EPA
1992a, A.I). In instances where heavy metals are complexed by hydrocar-
3.26
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Chapter 3
bons, some metals may also be removed from the solids (US EPA 1990b).
Treatment effectiveness can be increased by adding evaporation and extrac-
tion stages.
The process has been variously described as extraction (Trowbridge,
Holcombe, and Kollitides 1991), drying (Lau 1991), steam stripping (Haz-
ardous Waste Consultant 1991), and evaporative. It has been characterized
by the US EPA both as a "solvent extraction process" (US EPA 199la) and
as "other physical treatment" (US EPA 1991c). Because the main treat-
ment steps involve solvent extraction and water evaporation stages, the
process is addressed in this monograph. It should be noted that the carrier
solvent may be used in the very first stage or it may be mixed with the
waste in later evaporation and extraction stages after some evaporation has
already occurred (US EPA 1992a). The solvent aids in maintaining the
waste in a slurry state as water is evaporated, as well as serving as a me-
dium for the extraction of organic contaminants. The process consists of
the following steps (see figure 3.4 on page 3.28):
1. Pretreatment. Debris is separated from the feed, and if neces-
sary, the feed particles are ground to sizes less than 6 mm (0.25
in.);
2. Feedstock Slurrying (Fluidizing). The feed material is slurried in
a fluidizing tank with a carrier oil or solvent to extract indig-
enous oils and soluble organics. In general, the solvent-to-feed-
stock waste solids ratio varies from 5:1 to 10:1 by weight. The
exact solvent to be used depends on the site, but a hydrocarbon-
based solvent with a boiling point around 150°C (300°F) is used
for hydrocarbon or organically-contaminated solids (US EPA
1992d). According to DTC, alcohols or food-grade mineral oils
are typically used (US EPA 1992d). The product of this stage is
a slurry mixture;
3. Evaporation and Solvent Extraction Stages. The water in the
slurry is evaporated. In general, two to four multi-effect evapo-
rators are used in commercial systems to evaporate the water
(US EPA 1992d). Alternatively, mechanical vapor recompres-
sion may be used (Holcombe and Kollitides 1991). According
to DTC, lower temperatures can be used, if necessary, by operat-
ing under a vacuum (Trowbridge, Holcombe, and Kollitides
1991). For example, the evaporative stages can employ succes-
3.27
-------
Process Identification and Description
Figure 3.4
Carver-Greenfield Process Schematic
Steam ) f
Decontaminated
solids
product
Feed Vacuum
sludge/soil/ pump
E xtracted
o I soluble
contaminants
sive boiling chambers, each operating at progressively lower
pressures (Environment Today 1991). This allows succeeding
chambers to use less energy vaporizing the water (Environment
Today 1991). Removal of the water aids in breaking up emul-
sions, thereby increasing organic extraction. At the same time,
steam generated in the evaporation system removes water and
volatile compounds from the waste-solvent slurry (NETAC
1991; Hazardous Waste Consultant 1991). The heat also de-
stroys microorganisms. The products of these stages consist of
vapors and a water-free slurry of solids in carrier solvent;
4. Condensation and Oil and Water Separation (Vapor Treatment).
The vapors from the evaporation step are condensed. The water,
carrier oil, and solvent condensate are then sent to an oil and
water separator (decanter). The decanting separates any carrier
oil and solvent and water-immiscible solvents from the water.
3.28
-------
Chapter 3
The recovered water contains some residual solvent and low-
boiling point water-soluble compounds. The water is, however,
generally relatively clean and virtually free of solids and can
usually be treated with standard wastewater treatment technolo-
gies. Any recovered carrier oil can be recycled to the fluidizing
tank. The vent gases can be treated for residual organics by
granular activated carbon (US EPA 1992a);
5. Centrifuging (Water-Free Slurry Treatment). The majority of
the carrier oil and solvent is separated from the feed solids by
centrifuging. The solids may then be reslurried with clean (re-
circulated) solvent for additional extractions or be directed to
desolventization. The concentrate (from each extraction) gener-
ally consists of the carrier solvent (with extracted indigenous oil
and organics) and approximately 1% fine solids. The centrifuge
cake generally consists of 50% solids and 50% solvent with
extracted organics;
6. Desolventization of Solids (Treatment of Centrifuge Cake). The
solvent is removed from the solids by heating (evaporation) and
stripping by countercurrent contacting of the solids with gas (US
EPA 1992a). Earlier descriptions referred to this as a
"hydroextraction" or "vacuum hydroextraction" step (Holcombe
and Kollitides 1991) that heated the centrifuge cake under
vacuum (Bress, Greenfield, and Haug) and utilized steam to
contact the solids (US EPA 199la). More recent studies have
used nitrogen gas to strip the solids (US EPA 1992g). The re-
sulting offgas is then scrubbed to remove carrier oil/solvent and
recirculated. The vent gases can be treated for residual organics
by granular activated carbon (US EPA 1992a). Most of the
heavy indigenous oils in the centrifuge cake will remain with the
solids in the centrifuge cake, rather than evaporate (US EPA
1992d); and
7. Distillation of Carrier Oil/Solvent (Treatment of Concentrate).
The used carrier solvent is distilled to recover the carrier oil and
solvent and separate the indigenous oils and organics. Products
of this step consist of a recovered solvent (substantially free of
contaminants), which may be reused, and concentrated streams
of light and heavy organics, which may be incinerated or re-
claimed.
3.29
-------
Process Identification and Description
It should be noted that the above description pertains to the complete
Carver-Greenfield Process. Some designs incorporate only some of these
stages.
The pilot-scale plant that was used in some recent testing differs from the
commercial-scale systems that have been installed to treat other types of
wastes. For example, the commercial-scale systems generally operate con-
tinuously, while the pilot-plant extraction was conducted on a batch basis.
In addition, solvent distillation was not performed during pilot-scale tests
(because of the lack of pilot-scale distillation equipment). Therefore, new
solvent was used for each extraction. Finally, water evaporation was con-
ducted in a single-effect step.
3.10.2 Status of Development
The Carver-Greenfield Process was originally developed by Charles
Greenfield in the 1950s at the Carver Press Company laboratory (NETAC
1991). The first commercial plant was installed in 1961 to treat meat ren-
dering wastes (NETAC 1991), and the process has since been operated
commercially in the treatment of nonhazardous municipal and industrial
wastes (US EPA 1992a). Commercial-scale systems generally treat other
types of waste, and consequently, the capacity of the process for treating
soils and petroleum sludges has not been proved.
In recent years, tests have been conducted on drilling mud wastes from a
Superfund site, refinery slop oil, and petroleum sludge to determine whether
the process was suitable for treating soils and sludges contaminated with
organic compounds. Treatment of the drilling mud wastes was evaluated
under the US EPA's SITE Program in 1991 using a pilot-scale system (US
EPA 1992a). The pilot-scale system being used to test such materials, lo-
cated in New Jersey at the Dehydro-Tech corporate headquarters, has a
capacity of approximately 45 kg/hr (100 Ib/hr) (US EPA 1992a). A trailer-
mounted demonstration unit is available for on-site testing (Hazardous
Waste Consultant 1991).
Over 85 Carver-Greenfield plants have been licensed worldwide
(NETAC 1991); 53 of the facilities are designed to dry and deoil slaughter-
house wastes (US EPA 1992a). Commercial-scale units that have been
recently installed include the following treatment processes (NETAC 1991):
• petrochemical activated sludge with 15% solids (installed in
1980 in Italy, with a 6 dry tonne/day (6.5 dry ton/day) capacity);
3.30
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Chapter 3
• biosludge and wool scouring waste with 2% solids (1985, Vir-
ginia, 18 tonne/day (20 ton/day));
• dye wastes with 14.3% solids (1986, Soviet Union, 43 tonne/day
(48 ton/day));
• alum sludge with 3% solids (1987, California, 15 tonne/day (17
ton/day));
• undigested municipal sludge with 20% solids (1989, Japan, 45
tonne/day (51 ton/day));
• digested municipal sludge with 7% solids (1990, New Jersey, 45
tonne/day (51 ton/day)); and
• oily industrial sludge with 10% solids (1991, Italy, 3.8 tonne/day
(4 ton/day)).
When applied in drying wastes, the process can be used to produce fuel,
as well as to recover materials such as lanolin (Holcombe and Kollitides
1991).
3.10.3 Design Data
Design data for the Carver-Greenfield Process were gathered from sev-
eral sources, but much of the information was proprietary, and therefore,
not available for review. In an economic analysis based on operating data
from existing plants, the US EPA estimated that 1.7 billion Joule would be
used per tonne of waste (1.47 MM Btu/ton) in treating a waste consisting of
52% solids, 17% indigenous oil, and 31% water by weight. Nitrogen con-
sumption (for deoiling) was estimated at 45.9 standard mVhr (1,620 stan-
dard ftVhr). The process requires 480-volt, three-phase electric power (US
EPA 1992a). Typical operating parameters included the following: energy
consumption of 700 J/g to 1,200 J/g (300 to 500 Btu/lb) of water evapo-
rated; operating temperatures of 43° to 177°C (109° to 350°F), and operating
pressures of 13.8 to 34.5 kPa (2 to 5 psia) (NETAC 1991). According to
DTC, operating pressures may range from 10.3 to 103.5 kPa (1.5 to 15 psia)
(Trowbridge 1992).
The pilot-scale unit that has been used in recent treatability testing has a
capacity of 45 kg/hr (100 Ib/hr) (US EPA 1992a). The system has a nomi-
nal capacity of about 45 kg/hr (100 Ib/hr) of water evaporation and 180 kg/
hr (400 lb/hr)of solvent evaporation (Trowbridge, Holcombe, and Kollitides
3.31
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Process Identification and Description
1991). The centrifuge and desolventizer process solids at a rate of 13.6 kg/
hr (30 Ib/hr) (Trowbridge, Holcombe, and Kollitides 1991). In another
economic analysis, the US EPA postulated a commercial system could op-
erate at a capacity of 0.92 mVhr (1.3 ydVhr), (US EPA 1992d, 36).
Existing operating commercial units worldwide are used to convert
wastes to fuels (Holcombe and Kollitides 1991). Feed solids for these units
generally ranged from 2 to 20% (although one unit treated 40% solids and
another treated 10 to 50% solids) and treatment capacity ranged from 0.3 to
382 dry tonne/day (0.33 to 420 dry ton/day) (Holcombe and Kollitides
1991).
The commonly-used solvent Isopar-L, has a boiling point of 204°C
(400°F) (US EPA 1992a). Use of other solvents has been reported. For
example, iso-octanol was determined to be effective in extracting bitumen
from peat (Holcombe and Kollitides 1991). The solvent-to-feed ratio varies
with solids content and treatability goals. In one study, a 16:1 solvent-to-
solids ratio was used (see Case Study #2, Appendix C), which is higher
than the 5:1 to 10:1 sol vent-to-waste solids ratio guideline in US EPA docu-
ments (US EPA 1992a). In the US EPA SITE demonstration, a 10:1 ratio
of solvent-to-feedstock solids was intended (US EPA 1992a).
According to DTC, pilot-scale systems operate at temperatures of 65° to
93°C (150° to 200°F) in initial evaporation/extraction stages, increasing to
110° to 135°C (230° to 275°F) to evaporate water. At 180°C (360°F), carrier
solvent removal from solids in the desolventizer occurred (Trowbridge,
Holcombe, and Kollitides 1991).
See Appendix C for case studies which provide indications of tempera-
tures and other operating parameters. Case Study #2 reports on the treat-
ment of refinery slop soil at 80° to 110°C (180° to 230°F) with a vacuum of
280 mm of Hg (US EPA 1992d). The resulting solid samples were deoiled
at 149°C (300°F) and 737 mm of Hg vacuum. Solvent was evaporated from
the solvent and indigenous oil mixture at about 120°C (250°F) and 600 mm
ofHg.
In case Study #3, two stages of evaporation for treatability testing of a
petroleum sludge were simulated. The first stage operated around 66°C
(151°F) with a vacuum of 585 mm Hg. The second stage operated at 93°C
(200°F) with a vacuum of 280 to 305 mm Hg (US EPA 1992a). Following
3.32
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Chapter 3
evaporation, the solids were slurried with solvent, filtered, and then deoiled
in a vacuum oven at 120°C (250°F) and 710 mm of Hg (US EPA 1992a).
The commercial plant in Case Study #5, having five evaporation stages
treating wool scouring wastes, was designed with operating temperatures of
49°, 60°, 71°, 82°, and 127°C (120°, 140°, 160°, 180°, and 260°F) (US EPA
1992a).
3.10.4 Pre- and Posttreatment
Materials having a dimension greater than 6 mm (0.25 in.) cannot be
treated by the Carver-Greenfield Process, but may be ground to a treatable
size (US EPA 1992a).
In the US EPA SITE demonstration, the wastes were slurried with carrier
solvent in the first processing step. The developer, however, has described
commercial plants in which several evaporative stages involving slurrying
with the carrier solvent were conducted before the evaporative and extrac-
tive stage (see Case Study #5, Appendix C). As a result, evaporation or
dewatering may be considered a pretreatment step for some wastes.
The Carver-Greenfield Process produces the following residues:
• concentrated indigenous oil and organics. According to the
developer, this material can either be refined and reused or
burned (either for destruction or steam production) (US EPA
1992a);
• water, substantially free of solids and oils. Although the water is
described in reports as "substantially free" of solids and oils, it
will generally require further treatment. This can usually be
accomplished, however, by a wastewater treatment plant (US
EPA 1992a); and
• clean, dry solids. The solids may generally be used in landfills,
unless this is precluded by regulations or the presence of inor-
ganic compounds. If inorganic compounds such as metals re-
main, the waste may be subjected to further treatment such as
chemical fixation (US EPA 1992d). The removal of petroleum
contaminants can greatly improve the effectiveness of chemical
fixation (Holcombe, Cataldo, and Ahmad 1990). If the waste
feed is classified as hazardous, the treated solids must be charac-
terized prior to disposal (US EPA 1992a).
3.33
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Process Identification and Description
In addition to these residues, vent gases may require treatment, for ex-
ample, by granular activated carbon. The concentration of residual organics
on the solids will depend on such factors as the influent feed, the type of
extracting solvent, and the number of extraction stages (Holcornbe,
Trowbridge, and Rawlinson 1991).
The developer has described an example materials balance for the entire
system (based on tonne per day). For a 91-tonne feed consisting of 10%
solids, 40% oil, and 50% water, the materials generated or remaining after
each processing step were described as follows (Holcornbe, Trowbridge,
and Rawlinson 1991, 4):
• 49.5% removed from evaporation stage, consisting of 45 tonne
(50 ton) water;
• 36.5% removed as centrifuged concentrate, consisting of 33
tonne (36 ton) oil and 0.3 tonne (0.36 ton) solids;
• 14.0% removed as centrifuged solids, consisting of 8,8 tonne
(9.7 ton) solids, 3.5 tonne (3.8 ton) soil, and 0.5 tonne (0.6 ton)
water.
The centrifuged solids are desolventized, and makeup solvent (0.3 tonne)
is added, resulting in oil-free solids (8.8 tonne solids, 0.1 tonne solvent, and
0.5 tonne water) and oil (3.5 tonne oil and 0.2 tonne solvent) (Holcornbe,
Trowbridge, and Rawlinson 1991); and
According to DTC, in some instances, the solvent can be a partial cut of
the indigenous oil in the feed, which can be recycled within the system
(Trowbridge 1992).
3.10.5 Operational Considerations
The Isopar-L carrier solvent used in demonstrations of the Carver-
Greenfield Process is a food-grade isoparaffinic oil with a high boiling
point (204°C (400°F)) and low toxicity. Therefore, special handling is not
required (US EPA 1992a). Other solvents with boiling points between 180°
and 240°C (360° and 460°F) may be used; however, only iso-octanol has
been specifically identified (Trowbridge 1992). The extraction efficiency
can be expected to be increased by using particular solvents and additives
for particular feed wastes (US EPA 1992a).
Treated solids and contaminated-carrier solvent may be stored in 210 L
(55 gal) drums or other containers. Water may also be stored or. alterna-
3,34
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Chapter 3
lively, routed to a POTW. In the SITE demonstration, the final solids and
recovered water were basically free of toxic contaminants and therefore, no
special handling was required. The residual solvent, which contained ex-
tracted organics, required handling as a hazardous waste (US EPA 1992a).
3.10.6 Environmental Impacts
The Carver-Greenfield Process is designed to treat wastes on site. The
treatment of resulting wastewater and disposal of solids may take place on
site or off site (US EPA 1992a). If the original feed is a listed waste, solids
residues will be considered listed wastes. If the solids are not listed wastes,
they may require testing to determine whether they are RCRA characteristic
hazardous wastes. Land disposal regulations must be considered in dispos-
ing of these waste streams. Solvent may either be recycled or disposed, and
air emissions must be monitored (US EPA 1992a).
Potential environmental impacts include air emissions, dust releases, and
transportation issues (US EPA 1992d). The potential for air emissions is
mitigated because the process is closed. The developer observes that con-
cerns about air pollution, personnel safety, and odors are minimized be-
cause the process is "completely enclosed and operates under slight
negative pressure" (Holcombe, Cataldo, and Ahmad 1990). Fugitive dust
emissions can generally be mitigated (US EPA 1992a), although they re-
quire treatment of the final product with additives (Lau 1991). In sum, the
primary environmental impacts occur during removal of recovered indig-
enous oil and contaminated solvent from the site (US EPA 1992a).
3.11 Extraksol Process
3.11.1 Description
The Extraksol Process is carried out by a transportable system developed
by the Sanivan Group of Anjou, Quebec, Canada. The process uses propri-
etary solvents for batch extraction of contaminated soils. Organic contami-
nants are extracted in three phases: washing, drying, and solvent
regeneration (Mourato and Paquin 1990). See figure 3.5 (on page 3.36) for
a simplified process schematic.
3.35
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Process Identification and Description
Figure 3.5
Extraksol™ Process Simplified Process Schematic
Contaminated
solvent
— — — — Drying cycle
The extraction vessel is a mix tank without an internal agitator. The
extractor is loaded with solids, sealed, purged with an inert gas, and filled
with solvent. The extraction vessel is then rotated. Absence of an internal
mixing system, according to the developer, enables the system to process
large nonporous solids. Agitation, combined with the dewatering effect of
hydrophilic solvents, will fracture porous solids, reducing their size. After
each extraction, the vessel's rotation is stopped, and the solids settle to the
bottom. The contaminated solvent is decanted and pumped to a still for
solvent recovery, completing a wash cycle. Multiple wash cycles (extrac-
tion phases) may be required to meet cleanup requirements for certain con-
taminants. The number of wash cycles and the appropriate solvent, or blend
of solvents, to be used in treating a particular waste stream is determined by
bench and/or pilot tests.
The solids drying cycle begins with the draining of the solvent from the
extraction vessel through a geotextile filter. Plugging of this filter has not
been identified as a problem. This may be due to the fact that the Devel-
oper limits application of this technology to solids with no more than a 30%
3.36
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Chapter 3
clay fraction. The solids are heated by introducing hot nitrogen gas and
steam into the extractor. The extraction vessel is then rotated. The heated
gas strips the solvent from the solids, leaving a dry product. The exact
amount of steam to be introduced into the gas stream depends upon the soil
and contaminant characteristics. While the additional heat provided by the
steam aids volatilization, excess moisture complicates solvent removal and
solids drying. Gas is withdrawn from the vessel by vacuum and discharged
to a condenser. Condensed solvent and water are discharged to a contami-
nated solvent tank, while the gas stream flows into a gas holding tank where
it remains ready for reuse. At the completion of the drying cycle, the ex-
traction vessel is opened, and the dry solids are discharged to a transport
vehicle or conveyor system. The Extraksol unit, operating in the drying
cycle only, can be used as a thermal desorber to remove volatile contami-
nants from solids.
The solvent regeneration cycle begins with the pumping of the contami-
nated solvent from its holding tank to the distillation unit. The mixture is
heated to separate low-boiling point solvents from the high-boiling point
components. The low-boiling point components are volatilized, condensed,
and collected for reuse as clean solvent. The remaining liquid components
flow under gravity through a settling compartment within the distillation
unit. Liquid decanted from this vessel is discharged as wastewater and may
require further treatment. Still bottoms contain the concentrated organic
fraction. As this fraction accumulates, it is pumped to a residue holding
tank. It will require further treatment, such as incineration or
dehalogenation, depending upon its chemical makeup.
3.11.2 Status of Development
Bench-scale treatability tests are conducted to determine whether the
Extraksol Process is applicable to a particular waste stream (Mourato and
Paquin 1990). The bench-scale test, conducted in a 0.07 m3 (2.5 ft3) rotary
mixer, merely simulates the washing cycle. Solids are weighed and loaded
into the mixer, the vessel is purged with nitrogen, and a measured volume
of solvent is added. The vessel is then rotated in a movement similar to that
of the full-scale unit. The mixing time is equivalent to a wash cycle for the
full-scale unit. At the completion of a wash cycle, the solvent is sampled
and drained from the vessel. A fresh volume of solvent is added, and a
second wash cycle is initiated. Any number of wash cycles may be used,
3.37
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Process Identification and Description
although the Sanivan Group normally limits the number of extraction cycles
to nine. The cost of full-scale operations using more than nine wash cycles
may be prohibitive (Mourato and Paquin 1990).
In addition to the washing tests, the Sanivan Group normally performs
material behavior tests consisting of a soil-solvent reactivity test and a fil-
tration test. The soil-solvent reactivity test consists of immersing small
amounts of the test solids in a number of different solvents and observing
the results. If an emulsion forms, it is filtered through geotextile lo deter-
mine whether it will restrict solvent flow.
In the filtration test, performed in the rotary mixer, a geotextile filter is
placed over the mixer's drain. At the completion of a wash cycle, the sol-
vent is drained through this filter. The time required for the solvent to com-
pletely drain from the mixer is noted, along with the volume of solvent and
any obstructions and solids particles washing through the filter. A signifi-
cant amount of solids washing through the filter indicates that the process is
not suited to treat the matrix. The Sanivan Group has found that the
Extraksol Process is ineffective in treating soils with a clay content >40%
and a water content >30%.
The Sanivan Group has constructed two full-scale mobile systems. The
0.9 tonne/hr (1 ton/hr) system is operated with manual controls and is
housed on a single 2.4 m by 11 m (8 ft by 36 ft) trailer, may be used in pilot
testing, as well as in full-scale treatment. The advantage of using this sys-
tem as a pilot plant is that material-handling problems are easily identifiable
at this scale. Its use is restricted to on-site operations. Support equipment
is skid mounted and can be transported on two trailers. The system has
been used to treat PCB-contaminated soils; remove oil and grease from
refinery sludges, porous gravels, and Fuller's earth; and remove PCPs from
porous gravel and activated carbon. Descriptions of these operations have
not been published in the literature.
The 5.5 to 9 tonne/hr (6.2 to 10.1 ton/hr) system, constructed in 1991 but
not yet used, has an operating unit similar to that of the 0.9 tonne/hr system.
Twin extraction vessels are used in this larger, fully automated system. The
twin extractors are similar in appearance and operation to cement mixers.
Use of twin-batch extractors enables the loading of one extractor while the
second is going through its washing and drying cycles. The extractors share
a common solvent recovery system (Paquin 1992).
3.38
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Chapter 3
3.11.3 Design Data
The Extraksol Process is designed to use several proprietary solvents,
individually or blended. This flexibility allows selection of solvents that
have a high affinity for particular contaminants. Unit operations consist of:
• washer/dryer extraction;
• nitrogen gas blanketing;
• geomembrane filtration;
• steam generation;
• condensation (refrigerated); and
• solvent distillation.
The number of wash cycles and the wash cycle time may be varied to
more effectively remove particular contaminants from the solids. The
developer's data suggest that the efficiency in removing PCBs from clay-
bearing soils has not exceeded 97.6% (Mourato and Paquin 1990). This is
consistent with the developer's suggestion that the process should not be
used to treat soils with a clay content >40%. When PCB-contaminated
sands were treated, however, only a marginal improvement in removal effi-
ciency (98.6%) was observed (Mourato and Paquin 1990).
3.11.4 Pre- and Posttreatment
The process was designed to accommodate large nonporous solids, such
as rocks and stones, but porous material must be crushed and/or screened to
a particle size of less than 5.1 cm (2 in.) in diameter (US EPA 1992c).
Therefore, even though the extraction vessel can accommodate large solids,
screening and crushing operations required for particular waste streams,
may limit the usefulness of such a feature. In addition, dewatering may be
necessary before treating certain waste streams because the process is mois-
ture sensitive. Waste streams with a moisture content >30% can cause re-
duced removal efficiency, extended time required for solvent regeneration,
and increased volume of wastewater (US EPA 1991c).
Posttreatment concerns are essentially the same as those for the B.E.S.T.
Process, described in Subsection 3.8.4. The Sanivan Group has stated,
however, that chelating agents may be used with the solvent during the
wash cycles to mobilize lead (Mourato and Paquin 1990). Chelated lead
3.39
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Process Identification and Description
would be concentrated in the wastewater fraction requiring additional treat-
ment before disposal.
3.11.5 Operational Considerations
The 0.9-tonne/hr (1 ton/hr) system is relatively compact, occupying an
area less than 28 m2 (300 ft2), exclusive of support equipment. As was pre-
viously observed with the B.E.S.T. process, the restricted access zone stan-
dard (NFPA 1990) significantly expands the space requirements even for
such a compact system. Because of regulations which limit movement of
hazardous wastes between Canada and the United States, conducting
treatability tests for solid samples which originate in the U.S. may pose
some problems. Treatability testing using this system may require obtain-
ing an independent test facility within the U.S. No other unique operating
considerations have been identified.
3.11.6 Environmental Impacts
To minimize potential air emissions, process gases are vented through an
activated carbon filter before being released to the atmosphere. Process
wastewaters may contain low concentrations of organic and inorganic con-
taminants and therefore, may require additional treatment before being dis-
charged.
3.12 Low-Energy Extraction Process
3.12.1 Description
The following description of LEEP® is based primarily on information
provided by ART International, Inc.. The process uses organic solvents to
extract organic contaminants from soils, sediments, and sludges. Contami-
nants are leached from the solid matrix through use of a hydrophilic (water
miscible) leaching solvent and then concentrated using either a hydrophobic
(water immiscible) stripping solvent or distillation. ART International, Inc.
has developed two types of plant processes. The "LEEP-Tar-plant" is tar-
geted for coal tars and related compounds, while the "LEEP-PCB-plant" is
intended to treat PCBs and related compounds. The two plants have similar
3.40
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Chapter 3
mechanical configurations, but differ in solvent usage and recovery. Figure
3.6 presents simplified process flow diagrams for these two applications.
The process consists of the following steps:
1. Separation and Screening of Contaminated Materials. If feed
materials contain free water (moisture content exceeding 50 to
70%), the material is first separated by filtration or centrifuga-
tion into a solid and a liquid fraction. For the pilot-scale plant,
Figure 3.6
LEEP® Process Configurations
LEEP-Tar-Plant
LEEP-PCB-Plant
The shaded boxes indicate unit operations which would be substituted in the conversion of a LEEP-Tar-Plant
to a LEEP-PCB-Plant
LEEP is a registered trademark of ART International, Inc.
3.41
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Process Identification and Description
materials must be crushed to less than 6 mm (0.25 in.) size prior
to leaching. A commercial (full-size) plant which has been de-
signed, but not constructed, is designed as a closed loop system
capable of handling particle sizes up to 203 mm (8 in.) in diam-
eter. Solids are fed through a grizzly/vibrating screen which
rejects oversized (>203 mm (>8 in.)) material. The full-size
plant includes equipment to crush the solids to 13 to 25 mm (0.5
to 1 in.) size before the materials are fed to the leaching opera-
tion.
2a. Treatment of Solid Fraction. Leaching is performed at atmo-
spheric pressure in a continuous solid/liquid countercurrent
contactor. The leaching solvent in the PCB-plant is acetone, and
in the Tar-plant acetone and a proprietary hydrophobic solvent is
used. A number of additional leaching solvents have been tested
in bench-scale studies, but are not currently used in the LEEP®
process. The level of treatment is adjusted through modifying
the flow rate (and therefore the contact time), the revolutions per
minute, and/or the liquid to solid ratio. Products of the leaching
unit operation consist of clean solids (containing residual clean
leaching solvent) and contaminated leaching solvents (contain-
ing water, leaching solvent, and the removed contaminants).
2b. Treatment of Liquid Fraction. Any free water is treated through
a carbon adsorption water treatment system. The water may be
separately discharged or recombined with the soil following
completion of soil treatment.
3a. Treatment of Contaminated Leaching Solvents by Liquid-Liquid
Extraction or Distillation. For the PCB-plant, the contaminated
leaching solvent (acetone) is put in contact with the hydrophobic
stripping solvent (kerosene) in order to reduce the volume of
contaminated material. Products of the PCB-plant liquid-liquid
extraction operation consist of a cleaned leaching solvent and
water mixture, containing only trace amounts of contaminants,
and a small volume of contaminated stripping solvent (with the
majority of the contaminants). Any water leached from ihe con-
taminated solids is separated from the acetone by distillation and
treated by carbon adsorption in the water treatment system. For
the Tar-plant, the contaminated leaching solvents (acetone and
proprietary solvent) are separated from water and the contami-
3.42
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Chapter 3
nants by distillation. Recovered water is treated through carbon
adsorption.
3b. Residual Solvent Recovery (Processing of Cleaned Soils). In
order to remove residual solvent from the cleaned soil, the solids
are treated in a continuous dryer. Evaporated solvent vapors are
then condensed, collected, and recycled to the solvent feed of
the leaching unit. The soil is then recombined with the treated
water and the moist soil is discharged from the process.
4. Stripping Solvent Destruction and Coal Tar Recovery. For the
PCB-plant, the contaminant-laden kerosene is collected for off-
site disposal. For the Tar-plant, the refined tar from the distilla-
tion may be collected for potential commercial use.
3.12.2 Status of Development
The LEEP® was developed in 1987 by a New York University research
team in the course of a study funded by the US EPA (Steiner and Rugg
1992; Hall, Sandrin, and McBride 1990). The purpose of the study was to
develop a low-energy, cost-effective process for removing PCBs from con-
taminated soils, sediments, and sludges.
The process has been under commercial development by ART Interna-
tional, Inc. since June of 1988 (Rugg 1992). It was accepted by the SITE
Program as an emerging technology in June of 1989. By May, 1992, one
Canadian and three U.S. patents had been issued and other patent applica-
tions were pending (Steiner and Rugg 1992).
Bench-scale treatability studies have been conducted (see Appendix D)
and a pilot plant with a nominal throughput of 91 kg/hr (200 Ib/hr) was
completed in February of 1992. Pilot-plant studies are being conducted
under a RCRA permit and a Toxic Substances Control Act (TSCA) permit
(US EPA Region II) at the ART International, Inc. facility in New Jersey
(Steiner and Rugg 1992). Based on bench-scale and pilot-scale test results,
design criteria were prepared for a commercial-size LEEP-Tar-plant. The
developer anticipates a plant to be commercially operational by early 1996.
3.12.3 Design Data
Bench-scale treatability studies to develop full-scale system design pa-
rameters, using 3 to 4 kg of sample, are conducted by ART International,
3.43
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Process Identification and Description
Inc. The bench-scale studies include three leaching operation tests., one
liquid-liquid extraction test, and physical-chemical characterization of the
contaminated material (see Appendix D). The exact volume of material
required varies with the number of contaminant analyses and the moisture
content (Steiner and Rugg 1992).
A variety of leaching solvents have been tested during development of
LEEP®, including acetone, n-butylamine, diethylamine, and methylene
chloride (Steiner and Rugg 1992). The current leaching solvents which are
used by LEEP® include acetone (in the PCB-plant) and acetone mixed with
a proprietary solvent (in the Tar-plant). In addition to the leaching solvents,
contaminants are separated from the leachate with liquid-liquid extraction
using kerosene as a stripping solvent.
As observed in Subsection 3.12.2 a pilot plant which operates at a nomi-
nal throughput of 91 kg/hr (200 Ib/hr) is available for process testing. Pilot-
plant feasibility studies are necessary to determine site-specific throughput
rates. The rate of treatment will vary with the matrix type, contaminant
levels, and treatment requirements.
ART International, Inc. has developed design criteria for a commercial
size LEEP-Tar-plant, and plans additional pilot plant tests with PCB-con-
taminated soils in order to determine the design criteria for a LEEP PCB-
plant. The design capacity of a full-scale mobile Tar-plant process is 11.7
tonne/hr (13 ton/hr (dry)).
The planned commercial size plant is designed to operate at atmospheric
pressure and 54°C (130°F). Unit operations are blanketed with nitrogen.
According to the developer, the main vent stream is designed to be treated
with refrigeration and carbon adsorbers to maintain a near zero % hydrocar-
bon emission rate. Utility and other requirements are a function of plant
size, but are anticipated to be as follows:
• normal battery limit envelope of 1/2 acre;
• 500 to l,000hp;
• 8 to 12 million BTU heat load;
• cooling tower make-up of 10 to 20 gpm; and
• 10 to 20 SCFH nitrogen (depending on start-up and shut-down)
According to the developer, LEEP® can be applied to soil moistures of
25 to 35% without reducing throughput rates, and coal tar levels of at least
3.44
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Chapter 3
5% without on-site blending. Higher moisture and tar content soils may
also be processed by the unit, although treatment efficiencies will be af-
fected. The LEEP® process is not adversely affected by the presence of
cyanide or metals, although the process is not designed to remove these
constituents.
3.12.4 Pre- and Posttreatment
According to ART International, Inc., the commercial unit has been de-
signed with a front-end preparation section which can handle materials up
to 203 mm (8 in.) in diameter. The soil will then be crushed to 13 to 25 mm
(0.5 to 1 in.) in size prior to the leaching process. It should be noted that
the currently available pilot-scale process is limited to treating finer soils,
and cannot process materials exceeding 6 mm (0.25 in.). However, larger
materials can be crushed for pilot-scale testing. Due to economic consider-
ations, materials with free water (moisture content exceeding 50 to 70%)
are pretreated through centrifugation or filtration.
The residues of LEEP® are handled as follows:
• Clean Solids. The solids generated by the LEEP® plant consist
of a clean, moist, solid matrix which may be used as backfill.
• Treated Water. All of the water used in the system is eventually
treated by an adsorption unit. This includes the aqueous frac-
tion, which is initially separated from the solid matrix, and water
recovered from the water and leaching solvent mixture (after
evaporation of the mixture to recover the solvent). Water treated
by the LEEP® adsorption unit may require further treatment
steps to ensure that all contaminants of concern are removed.
According to the developer, additional water treatment unit op-
erations may be incorporated into the LEEP® system.
• Contaminated Stripping Solvent. The contaminants are concen-
trated in the stripping solvent. The contaminated stripping sol-
vent may be collected for off-site treatment (incineration) or in
some cases for reuse.
The leaching solvent is recycled. No information was available regard-
ing potential contaminant releases to the air during processing of the con-
taminated soils. According to ART International, Inc., however, the system
is designed as a closed system which is blanketed with nitrogen. This blan-
3.45
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Process Identification and Description
ket carries residual leaching solvent through condensers and a carbon ad-
sorption system prior to discharge to the atmosphere. The developer, there-
fore, does not expect contaminants to escape. It should be noted that
treatability testing should be conducted on sample soils in order to identify
residue problems specific to a site.
3.12.5 Operational Considerations
As with other innovative technologies, bench- and pilot-scale studies
should be conducted to determine the potential effectiveness of the process
in treating wastes at a particular site. Effectiveness of the LEEP® depends
on the particular matrix, as well as the type and level of contaminants
present. The rate of treatment (throughput) is affected by both the contami-
nant-leaching rate and the particle-settling rate. The throughput, in turn,
affects costs.
Therefore, the key information required is the characterization of the
matrix (percent moisture, particle size), type and level of contaminant (site-
specific), and required treatment levels.
The reagents used in this process (acetone and kerosene) are highly flam-
mable. Therefore the design and operation of the system must include mea-
sures to minimize the potential for fires.
3.12.6 Environmental Impacts
Detailed information concerning effects of the process on air, water, and
land was not available. The developer claims that no contaminant releases
are expected because the system is closed. Bench-scale test data indicate
the process will result in clean soil and water discharges.
A potential environmental impact may arise from the initial material
preparation and crushing activities. However, the developer indicates that
this front-end treatment will be conducted under a slight negative pressure
in order to control dust and fugitive emissions to meet regulatory require-
ments.
The final stripping steps for both the soil (solvent evaporation) and water
(adsorption unit) must be carefully monitored to assure that the soil and
water residues do not release leaching or stripping solvents at the site. As
described in Case Study #1 (Appendix D), some solvent schemes may re-
duce specific contaminants, but elevate levels of other compounds
3.46
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Chapter 3
(semivolatile remnants and other TICs). Consequently, treatability testing
should be conducted. When the leaching solvent is successfully removed
from soil residues, it is not expected to have significant environmental im-
pact because it is recycled within the system. The stripping solvent (which
contains the removed contaminant) is collected for off-site destruction (in-
cineration). Thus, if performed with sufficient care, this stage poses no on-
site environmental threat. There is, however, potential for off-site impact in
the form of air emissions resulting from incineration of the removed con-
taminants.
3.13 NuKEM Development Process
3.13.1 Description
NKD, a division of American NuKEM, has under development two
waste treatment processes employing solvent extraction. One process, tar-
geted primarily at remediation of contaminated soil, employs mixer/settlers
for the extraction operation (Massey and Darian 1989). The second pro-
cess, targeted at wastewaters and sludges from petroleum refineries, em-
ploys a continuous extraction column (Massey and Darian 1990).
Figure 3.7 (on page 3.48) provides a schematic diagram for the
contaminanted soils process. In the initial step, contaminated soil is fed to a
mixer where it is combined with a proprietary solvent and a proprietary
chemical reagent. Depending on the type of soil, the solvent-to-soil ratio
varies from a typical ratio of 1:1 to a maximum of 2:1 by weight. The slur-
ried soil leaving the mixer is fed to a countercurrent extraction unit employ-
ing mixer/settlers. In this unit, the soil is countercurrently combined with
solvent, and the organic contaminant is progressively removed as it passes
through the extraction stages. The number of extraction stages employed is
determined by the degree of decontamination desired. Three to five stages
of extraction are normally adequate to reach target levels.
The treated soil leaving the last stage of the countercurrent extraction
unit is fed to a solvent dryer in which the solvent is volatilized from the
soil, condensed, and recycled, either to the initial feed treatment step or to
the last stage of the extraction unit. The system is intended to be transport-
3.47
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Process Identification and Description
Figure 3.7
NKD Process Schematic — Contaminated Soils
T
Decontaminated
soil
able and would normally be operated on site. Accordingly, the treated soil
leaving the solvent dryer would normally be stored in a product storage
area, checked for quality, and returned later to the excavation from which
removed.
The contaminated solvent (extract) is withdrawn from the first mixer/
settler and is processed in a distillation unit in which the contaminants are
separated from the solvent. The recovered solvent is recycled to the initial
feed treatment step. The residual contaminants can be either destroyed on
site or, more typically, put in drums in a concentrated form and shipped to
an incinerator for destruction (Massey and Darian 1989).
A variation of the process is under development for treatment of refinery
waste streams having RCRA waste codes K048, K049, K050, K05 I, and
K052. This process is designed to directly treat raw refinery oily wastes, no
pretreatment being required. The vast majority of refinery oily wastes exist
as bulk water streams containing small amounts of oil and solid. Under
3.48
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Chapter 3
most processes, these streams are dewatered before treatment, an unneeded
operation under the NKD Process. In this variation (see figure 3.8), extrac-
tion is carried out in a multistage column extractor. Raw sludge (70% wa-
ter, 15% solids, 15% oil) is combined with a small amount of refinery-based
solvent and an unspecified amount of the proprietary reagent. This mixture
is fed at the top of a multistage, liquid-liquid countercurrent extraction col-
umn. For a 38 L/min (350 bbl/day) plant, this column would be 76.2 cm
(30 in.) in diameter and 10.7 m (35 ft) in height. Solvent is fed at the bot-
tom of the extraction column at a nominal flow rate of 75 L/min (20 gal/
min). Solids and water flow down the column, while solvent flows from
the bottom to the top, extracting oil from the refinery waste as it rises. The
oil-laden solvent (extract) exits the top of the column, while oil-free solids
and water exit the bottom. The solids and water (raffinate) from the bottom
Figure 3.8
NKD Process Schematic — Oily Waste
Solvent
distillation
Reboiler
Decontaminated
solids
Filter
3.49
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Process Identification and Description
of the extraction column are pumped to a solvent stripper (residual solvent
removal operation in figure 3.8 on page 3.49) in which residual solvent is
stripped from the mixture. The resulting slurry of solvent-free solids and
water is then pumped to a filter. Water from the filtration step is sent to the
refinery's wastewater treatment system, and the filter cake is accumulated
in a roll-off bin for shipment to a disposal site for stabilization, if necessary,
and then to landfills (Massey and Darian 1990).
The extract is fed to a fractional distillation column for the recovery of
the solvent. Reasonable recoveries are achieved at a reflux ratio of about
unity. Recovered oil from the reboiler is recycled to the refinery crude oil
fractionation unit, coker, or fluidized catalytic cracker.
One option, which greatly simplifies the process, is to return the extract
directly to the refinery crude oil fractionation unit. If this is done, the sys-
tem would not include a solvent distillation unit; the refinery would provide
fresh solvent and would receive back the oil-laden extract stream.
NuKEM Development states that in general, solvent extraction processes
tend to operate much less efficiently in the presence of water than in its
absence. The difficulty increases greatly when such processes are used to
treat soils containing >10% water. The water, soil, and solvent tend to form
emulsions and either agglomerate or coat the walls of the process vessels.
Consequently, the solvents do not adequately contact the soil and do not
effectively extract the contaminants. NuKEM Development claims to have
solved this problem by adding a small quantity of a proprietary reagent to
the soil in the initial process step.
3.13.2 Status of Development
As of August 1989, NKD was conducting pilot-scale studies on its soil
decontamination process at its Houston facility (Massey and Darian 1989).
In October 1990, pilot-scale efforts were underway on the refinery waste
version of the technology. A 480 L/day (4 bbl/day) pilot plant was being
operated in Houston (Massey and Darian 1990). See Appendix E for a
report of the treatability studies' results of the NKD Process.
3.13.3 Design Data
Very little design data on the NKD Process are available. Pilot-plant
operation of the refinery waste process employed a 7.6 cm (3 in.) diameter,
3.50
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Chapter 3
continuous, counter-current extraction column containing a total of 36 actual
extraction stages in an overall column height of 1.2 m (4 ft). The through-
put rate was 320 to 640 L/day (2 to 4 bbl/day), but apparently the system
was operated at higher rates from time to time. A feed rate of up to about
75 L/hr (690 bbl/day) is reported elsewhere (Massey and Darian 1990).
Based on the pilot-plant study results, NKD has projected the key fea-
tures of a process to treat the oily wastes from a 16 MM L/day (100,000
bbl/day) oil refinery. Raw API separator sludge and DAF sludge produc-
tion would be 9,100 tonne/yr (10,000 ton/yr) and slop oil production would
be 910 tonne/yr (1,000 ton/yr). The operation would require 160,000 L
(42,000 gal) of storage for sludge and 16,000 L (4,200 gal) for slop oil.
Sludge would be drawn from the storage tank at about 38 L/min (10 gal/
min) for about four days per week. During the fifth day, slop oil would be
processed at rates ranging from 3.5 to 19 L/min (1 to 5 gal/min), depending
on the characteristics of the sludge. The remaining days of the week would
be devoted to peripheral activities, including recharging the storage tanks,
characterizing the next feedstock, and establishing parameters for the next
week of operation.
The process flows as depicted in figure 3.8 (on page 3.49) would have
the following flowrates when operating on the sludge stream at 38 L/min
(10 gal/min). The solvent extraction column would be 0.76 m (2.5 ft)in
diameter and 10.8 m (35.4 ft) in height. Solvent would be injected into the
base of the column at a nominal flow rate of 76 L/min (20 gal/min).
The distillation column for fractionation of the extract has not been
sized, but would operate at a reflux ratio of near unity and would have a
heat duty in the 1,582 to 2,637 Joule (1.5 to 2.5 MM Btu/hr) range, with the
exact value depending on the degree of heat integration employed. Alterna-
tively, the extract could be returned to the refinery crude oil fractionation
unit, simplifying the process (Massey 1990; 1992).
3.13.4 Pre- and Posttreatment
Excavated soil is screened to remove bulk rock, tree stumps, and debris
of like size. The remaining soil is reduced to <5 cm (2 in.).
The soil remediation process produces clean soil and two by-product
streams. One by-product is debris and the other is the concentrated organic
waste, including the PCBs. Originally sold as a mixture with oil, PCBs are
3.51
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Process Identification and Description
generally recovered as a similar mixture. This stream usually is a liquid.
Most remediation sites also contain other organics, and all organics with
vapor pressures less than that of the solvent should appear in the concen-
trated waste stream. It is possible that very light organic compounds could
be present, and that these could build up in the solvent stream, which is
recycled within the process. If this happens, it might be necessary to purge
some of the solvent from the process (Massey and Darian 1989).
For the refinery waste treatment process with a feed rate of 2,268 kg/hr
(5,000 Ib/hr) of sludge and 34 kg/hr (175 Ib/hr) of solvent, the following
streams are expected:
• recovered oil (374 kg/hr (825 Ib/hr) of which 340 kg/hr (750 lb/
hr) is oil and 34 kg/hr (75 Ib/hr) is solvent);
• filtered water (1,361 kg/hr (3,000 Ib/hr)); and
• filtered solids (567 kg/hr (1,250 Ib/hr), of which 340 kg/hr (750
Ib/hr) are solids and 227 kg/hr (500 Ib/hr) is water).
Again, it is possible that high-volatility compounds could build up in the
solvent stream (Massey and Darian 1990).
3.13.5 Operational Considerations
The initial goal of the NKD development effort was to extend the
company's capability for treating PCB-contaminated soils and sludges. The
technology was to be capable of achieving treated soil PCB levels of less
than 2 ppm and be highly mobile rather than merely portable. Other goals
were that the process be simple, scalable, and economical in treating small,
as well as large, quantities of contaminated soil. At the time the develop-
ment effort was begun, it was felt that the problem of handling high-mois-
ture content soils was unsolved. NKD believes their process is capable of
handling soils with a wide range of naturally-occurring moisture content as
if no moisture were present (Massey and Darian 1989).
No unusual health considerations are evident. Exposure of employees to
the waste and to the refinery-derived solvent should be minimized. The
proprietary reagent used is said to be nontoxic and safe to handle:. The sol-
vent is flammable; process equipment should be designed and operating
procedures devised accordingly.
3.52
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Chapter 3
3.13.6 Environmental Impacts
The process does not appear to have potential for any unusual impact on
the environment. The solvent employed must be handled properly and stor-
age tanks must have appropriate venting devices. To prevent contamination
of nearby aquifers, the solvent must be thoroughly stripped from the treated
soil before it is placed back into the excavation site. With a properly de-
signed process, solvent losses to the atmosphere, soil, or aquifers should not
be significant. Proper solvent handling, secondary containment, and other
appropriate design features should mitigate impacts on the soil and the
groundwater in the vicinity of the operation.
3.14 Soil Restoration Unit
3.14.1 Description
Terra-Kleen Corporation developed a Soil Restoration Unit (S.R.LJ.) that
uses up to 14 different organic solvents in treating contaminated solids.
The solvents to be used in extracting organic contaminants from a particular
waste stream are determined through a series of bench-scale treatability
tests. The solvent is selected based upon the solubility characteristics of the
contaminant(s) and its phase separation characteristics with respect to the
solid matrix (Cash 1991).
The process steps are the same as those of the Extraksol Process: wash-
ing, drying, and solvent regeneration. The S.R.U. Process, unlike a batch
process, conveys the solids through a specially-designed extraction unit
where they are mixed with solvent(s) (see figure 3.9 on page 3.54). Con-
veyors are used to move solids from the solids feed hopper to the extractor
and then on to a solids drying unit. Fresh solvent continuously circulates
through the extractor. As the solvent mixes with the solids, organic sub-
stances are solubilized and removed. Continuous flushing of the contami-
nated solvents with fresh solvent causes solute concentrations in the solids
to equilibrate at a low level with solute concentrations in the liquid. Since
fresh solvent has no solute (organic contamination), removal is limited by
diffusion or desorption of the contaminants from the solid particles. Extrac-
3.53
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Process Identification and Description
Figure 3.9
Terra-Kleen Soil Restoration Unit Process Schematic
Decontaminated
solids
tion time can be adjusted to optimize removal efficiencies and minimize
processing time.
The solids drying unit is designed to remove residual solvent and pro-
duce a clean, dry product. The drying chamber is an enclosed tube through
which a heated air and nitrogen mixture is blown. Solvent vapors vented
from the dryer are condensed and drain to the solvent regeneration system.
Toward the end of the drying cycle, dried soil particles may become air-
borne. When this occurs, the air and vapor flow can be diverted through a
bag filter located ahead of the condenser. The filtered and condensed gas
stream is reheated and reused as feed gas for the dryer. Baghouse dust is
discharged as a clean solid.
3.14.2 Status of Development
Terra-Kleen Corporation uses a bench-scale S.R.U. for treatability test-
ing. Solids are loaded into an extractor, the extractor is sealed, and solvent
is circulated through the extractor. The extraction solvent is sampled at
3.54
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Chapter 3
specified intervals and analyzed for contaminant(s) content. When the sol-
vent samples show no detectable concentration of contaminant(s), the solids
are sampled and analyzed. Up to 14 different solvents or solvent blends can
be used during the test.
In 1988, the Terra-Kleen Corporation built a trailer-mounted pilot-plant
system that was designed to remove organic contaminants from soils. This
system, used in a Superfund removal action at the Traband site in Okla-
homa, served as the prototype for the S.R.U. and has since been dismantled
(Cash 1991, 1992).
The Terra-Kleen Corporation has designed and constructed a self-con-
tained mobile S.R.U. capable of treating up to 1.8 tonne (2 ton) of contami-
nated solids per hour. The mobile unit is housed within two enclosed 2.4 m
by 12 m (8 ft by 40 ft) trailers and carries out all process operations —
washing, drying, and solvent regeneration. Support equipment consists of
solvent holding tanks, solids classifiers, premixing tanks, and an auxiliary
distillation system, the need for which depends on the particular site.
A full-scale system was completed in the spring of 1992. It was sched-
uled to treat approximately 2,700 tonne (3,000 ton) of soils contaminated
with PCBs and chlorobenzenes at the Pinette Salvage Yard Superfund Site
in Washburn, Maine. During the summer and early autumn of 1992 the
S.R.U. was operated at the Pinette Salvage Yard Superfund Site. Soils
contaminated with PCBs were treated to achieve a clean up goal of 5 mg/
kg. This goal was achieved; however, the design throughput for the unit
was never realized. This was due to a series of problems which plagued the
operation. Oblong-shaped rocks, which were approximately 5 cm in diam-
eter and 7 to 15 cm in length, passed through the soils screens and broke the
conveyor system. Several days of operation were lost while the system was
repaired. Fines from the solids did not separate from the solvent during the
settling phase. Therefore, the developer had to replace the settling chamber
with a second unit which had a greater capacity. A polymer feed system
was also added which aided in flocculation and settling of the fines. Fi-
nally, the drying system did not remove all of the residual solvent from the
treated solids, and landfarming techniques had to be used to biologically
degrade the residual solvent before the treated soils could be returned to the
site.
Terra-Kleen has examined the operating problems which were experi-
enced at the Pinette Salvage Yard Superfund site and has designed a new
3.55
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Process Identification and Description
solvent extraction system. This system is batch fed, to eliminate material
handling problems, and uses a vacuum-extraction system to remove residual
solvent from treated solids. A SITE demonstration of this technology was
planned for the summer of 1994.
3.14.3 Design Data
In addition to using up to 14 different solvents and solvent blends, ac-
cording to Terra-Kleen Corporation, the S.R.U. can use washing fluids that
use surfactants and/or chelating agents for mobilizing inorganic contami-
nants such as metals (US EPA 1991c). The following are the unit opera-
tions:
• solvent/solids premixing;
• continuous solvent flow extraction;
• heated air/nitrogen drying;
• condensation;
• bag filtration;
• solvent settling;
• solvent filtration; and
• distillation.
The specific solvent(s) to be used and the time required for extraction of
particular wastes is initially determined through treatability tests. But the
regime can be adjusted based upon results observed during operation. A
pilot-scale prototype was used in treating PCB-contaminated sandblasting
sand at the Traband site in Oklahoma. A cleanup goal of less than 100 ppm
PCBs was established for the three sand piles at the site. Analysis of
samples from each sand pile revealed that concentrations of PCBs before
treatment were 4,600, 3,300, and 88 ppm. Following treatment, the concen-
trations of PCBs in composite samples were 94, 47, and 4 ppm (Cash 1991).
3.14.4 Pre- and Posttreatment
This process is designed to accommodate solids up to 7.6 cm (3 in.) in
diameter. Therefore, before a particular waste stream is treated, solids may
have to be screened and/or crushed. The size of the solids particles within
3.56
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Chapter 3
the extractor will be further reduced by solvent dewatering and by mechani-
cal forces of the material handling equipment. Additionally, waste streams
with high-contaminant concentrations (>3,000 ppm of a particular contami-
nant) may require premixing with the selected solvent (Cash 1992).
Premixing effects intimate contact between the solids particles and the sol-
vent, thereby reducing the overall time required for extraction.
The moisture content of a particular waste stream may also affect extrac-
tion of organic contaminants. High-moisture content solids (>30%) can
dilute hydrophilic solvents, thus reducing their effectiveness in solubilizing
organic contaminants. Furthermore, since distillation is employed to sepa-
rate water from solvent, the higher the initial moisture content, the greater
the energy required for separation.
Solids discharged from the S.R.U. are dry, but some residual solvent and
organic contamination may remain. Solids meeting cleanup criteria may be
returned to the land for reuse. Since beneficial organic matter may also be
removed by the extraction process, augmentation of the treated solids with
organic substrate may be necessary to promote degradation of residual sol-
vent. Inorganic contaminants are not removed from solids when organic
solvents are used for decontamination, and therefore, the solvent-extracted
solids may need to be treated by some other technique, such as stabilization/
solidification or soil washing (Meckes et al 1992; US EPA 1990c).
However, the Terra-Kleen Corporation has stated that chelating agents
may be used with the solvent during the wash cycles to mobilize metallic
contaminants. Chelated metals would be concentrated in the wastewater
fraction, which would require additional treatment before disposal.
Water produced through this process should be analyzed for the
contaminant(s) of concern and residual solvent. Low concentrations of
organic contaminants may remain with the water fraction. These contami-
nant concentrations may be sufficiently low to permit discharge to a POTW.
Liquid-phase carbon adsorption may be used to produce an aqueous dis-
charge free of measurable organic contaminants.
Organic contaminants are concentrated in the still bottoms. If chlori-
nated hydrocarbons, such as PCBs and some pesticides, are among the con-
taminants of concern, the treatment options are incineration or
dehalogenation. If chlorinated hydrocarbons are not among the contami-
nants of concern, the concentrated waste stream may be recycled.
3.57
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Process Identification and Description
3.14.5 Operational Considerations
The 1.8 tonne/hr (2 ton/hr) system is relatively compact, occupying an
area of approximately 93 m2 (1,000 ft2), exclusive of support equipment.
Use of an auxiliary distillation unit can add an additional 37 m2 (400 ft2) to
the siting requirements (Cash 1991). The solvents used are flammable;
therefore, NFPA standards are applicable. No other operational consider-
ations have been identified for this system.
3.14.6 Environmental Impacts
Because of similarities in the process design and solvents employed,
environmental impacts of the S.R.U. are expected to be essentially the same
as for the Extraksol Process (see Subsection 3.11.6).
3.58
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Chapter 4
4
POTENTIAL APPLICATIONS
Solvent/chemical extraction (SCE) processes have been selected by the
U.S. Environmental Protection Agency (US EPA) for some Superfund sites
contaminated with organics such as polychlorinated biphenyls (PCBs),
volatile organic compounds (VOCs), and pentachlorophenol. The SCE
processes discussed herein were developed to treat a wide range of organic
contaminants in several different matrices. See table 4.1 (on page 4.2) for a
summary of the types of contaminants removed in bench-, pilot-, or demon-
stration-scale testing by the processes reviewed. The development of these
processes has typically proceeded from a design addressing a particular
problem (PCBs in sediments) to a more general design capable of treating a
wide range of contaminants and matrices.
4.1 Basic Extractive Sludge Treatment
Process
Numerous Basic Extractive Sludge Treatment (B.E.S.T.) Process bench-
scale treatability tests have been conducted on soils, sludges, and sediments
contaminated with PCBs, polyaromatic hydrocarbons (PAHs), pesticides,
and other semivolatile and volatile organic contaminants. The results show
that highest removal efficiencies were achieved in treating solids that had
high initial concentrations of organic contaminants. In many cases, how-
ever, the treated solids retained a significant amount of the initial contami-
nant. For example, tests of three harbor sediment samples contaminated
with PCBs in concentrations of >20,000 mg/kg resulted in removal efficien-
cies of >99.8% after three extraction stages, but with residual PCB concen-
trations in the solids from 27 to 720 mg/kg. On the other hand, treatment of
two sediment samples having initial concentrations of PCBs of 83 and 68
mg/kg resulted in removal efficiencies for both samples of 99.6% and re-
4.1
-------
Potential Applications
Table 4.1
Potential Applications
Commercial Solvent/Chemical Extraction Processes
Contaminant Type
Matrices Tested
PCBs
PAHs
VOCs
Semi-VOCs
Pesticides
Pentachlorophenols
Soils (sands, loams, clays)
Sediments
Sludges
Slurries
Wastewaters
Drilling cuttings
Petroleum-listed wastes
K044 - K052 wastes»
BTX
Dioxins
Diesel fuel
Petroleum Hydrocarbons
K044 - K052 are RCRA waste codes
sidual PCB concentration in solids of 1.1 and 1.8 mg/kg. All of this points
to the need to conduct treatability tests before selecting this technology for
site remediation.
The B.E.S.T. Process may also be used in treating sludges from petro-
leum refineries and petrochemical operations, including Resource Conser-
vation and Recovery Act (RCRA) waste codes K044 through K052,
inclusive.
4.2 CF Systems
The CF Systems's supercritical technology uses liquefied gases as ex-
tracting solvents to remove organic contaminants, such as hydrocarbons and
oil and grease, from wastewaters, sludges, sediments, and soils. Carbon
dioxide is generally used for aqueous solutions, such as process water and
wastewater. Light hydrocarbons are recommended for sludges, sediments,
and soils. Supercritical technology can be applied to a large variety of or-
4.2
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Chapter 4
ganic contaminants, including carbon tetrachloride, chloroform, benzene,
naphthalene, gasoline, vinyl acetate, furfural, organic acids, dichloroethane,
oil and grease, xylene, toluene, methyl acetate, acetone, alcohols, phenol,
aliphatic and aromatic hydrocarbons, and PCBs.
CF Technologies, Inc. is now commercializing supercritical fluid extrac-
tion and has described possible applications encompassing solid and semi-
solid waste treatment, wastewater treatment, and pollution prevention,
including the following:
• removal of PCBs from contaminated soil;
• extraction of benzene, toluene, xylene (BTX) in wastewater
from petrochemical storage tanks and oil and water separators;
• separation of pesticides from contaminated soil;
• extraction of oil, lubricants, and PAHs from solids and ground-
water at synthetic gas and aircraft or automotive maintenance
facilities;
• recovery of certain Comprehensive Environmental Response,
Compensation, and Liability Act/National Priorities List
(CERCLA/NPL) pollutants, i.e., methyl methacrylate and tetra-
ethyl lead; and
• substitution for chlorofluorocarbons (CFCs) and chlorinated
solvents in cleaning and degreasing operations.
4.3 Carver-Greenfield Process
The Carver-Greenfield Process can be used to remove oil-soluble organ-
ics from soils, sludges, and other wastes, as well as to dry aqueous mixtures
(NETAC 1991). As noted in the US EPA Superfund Innovative Technol-
ogy Evaluation (SITE) Program report (US EPA 1992a), the process can be
used to treat wastes contaminated with organics, especially wastes with
high-water content.
The developer states that Carver-Greenfield has a new approach for
remediating soils, petroleum K-wastes, spent drilling muds, and hazardous
sludges containing petroleum-based contaminants, such as fuel oils, PCBs,
4.3
-------
Potential Applications
and polynuclear aromatics (US EPA 1992a). It should be noted, however,
that most commercial units are designed to treat high-water content wastes.
According to Dehydro-Tech Corporation (DTC), existing units "have pro-
cessing requirements very similar to oily soil/sludge treatment," and DTC
observes that dewatered municipal sewage sludge typically contains over
20% solids and has a high-ash content (US EPA 1992a). But, it should also
be noted that most contaminated soils and sludges are expected to have a far
higher solid content than that of municipal sewage sludge, and the potential
effectiveness of the Carver-Greenfield Process in treating low-water content
wastes must be investigated further.
Laboratory-scale tests have been conducted on solids from a site con-
taminated with diesel fuel and PCBs, as well as on mixed wastes (see Ap-
pendix C for case studies). In addition, pilot-scale studies have been
conducted on oily drilling mud wastes. Commercial units have treated such
materials as municipal and industrial sewage sludges, meat rendering waste,
wool scouring wastes, petrochemical sludges, wood pulp wastes, dairy and
food products, textile and dye wastes, paper mill sludge, brewery treatment
plant sludge, animal manure (for fertilizer production), and pharmaceutical
wastes. The soils and sludges process is intended mainly to treat those
contaminated with oil-soluble hazardous contaminants, including PCBs,
PAHs, and dioxins (US EPA 1991b; US EPA 1989).
Some commercial units incorporate portions of the Carver-Greenfield
Process designed for unique applications. For example, oily slops and slud-
ges from refineries may be disposed of by injecting them into coker feed.
In one design, this method was modified by dewatering the sludge with the
Carver-Greenfield Process, prior to coking it. In such a system, before
centrifuging the solids or recovering the oil, the oil-solid slurry direct from
the evaporative/extraction stage is sent to the delayed coker. The carrier oil
may later be recovered from the coker vapor products (Elliot 1992).
4.4 Extraksol Process
The developer states that the Extraksol Process can effectively treat soils
that have a maximum clay fraction of 40% and a maximum water content of
30% (Paquin 1992).
4.4
-------
Chapter 4
The number of wash cycles and the wash cycle time may be varied to
effectively remove certain contaminants from solids. The developer's data
suggest that efficiencies in removing PCBs from clay-bearing soils has not
exceeded 97.6% (Mourato and Paquin 1990). This is consistent with the
developer's suggestion that soils with clay contents >40% should not be
treated by this process. But, only a marginal improvement in efficiency
(98.6%) was noted when PCB-contaminated sands were treated by this
process.
Refinery sludges were also treated to remove oil and grease with effi-
ciencies of up to 99%. Similar results were obtained in removing grease
and oil from contaminated Fuller's earth. Oily sludges contaminated with
PAHs were also treated; removal efficiencies of up to 96% were reported,
with a final PAH concentration of 10 ppm. Pentachlorophenol-contami-
nated gravels and activated carbon were also treated using the 0.9 tonne/hr
(1 ton/hr) system, with removal efficiencies of >99.7% in the case of gravel
and 89% for carbon (Mourato and Paquin 1990). Other results indicate
considerable variability in efficiencies in removing oil and greases and in
removing particular contaminants. Therefore, site-specific treatability test-
ing is encouraged before the Extraksol Process is used in site remediation.
4.5 Low-Energy Extraction Process
The Low-Energy Extraction Process (LEEP®) is designed to treat coal
tars and PCB-contaminated materials. The process may also be used to
remove other organic pollutants such as petroleum hydrocarbons, PAHs,
pesticides, wood-preserving chlorophenol compounds from contaminated
soils, sludges, and sediments (Steiner and Rugg 1991). Materials that have
been treated by LEEP® include river and harbor sediments, sandy topsoil,
clay subsoil, and foundry sand. As noted by ART International, Inc., the
system developer, an advantage of the system is its ability to treat materials
having moisture content ranging from a few percent to >90% (Steiner and
Rugg 1992).
4.5
-------
Potential Applications
4.6 NuKEM Development Process
For the soil remediation version of the NKD Process, results have been
published only on the removal of PCBs from soils and sludges. It is ex-
pected, however, that the process will be effective in removing a wide range
of volatile organics, semivolatile organics, pesticides and their intermedi-
ates, petroleum hydrocarbons, and other organics. The petroleum refinery
sludge treatment version has been shown to be effective in treating API
separator sludge (US EPA waste code K051), dissolved air flotation (DAF)
float (US EPA waste code K048), and slop oil sludge (including US EPA
waste code K049). The process is expected to be effective in treating other
refinery waste sludges (Massey and Darian 1989,1990; Massey 1992).
4.7 Soil Restoration Unit
No operating data are available for the full-scale Soil Restoration Unit
(S.R.U.), and data available on the process are limited. A pilot-scale proto-
type was used in treating PCB-contaminated sandblasting sand at the
Traband site in Oklahoma. A cleanup goal of a concentration of <100 mg/
kg PCBs was established for the three sand piles at the site. Analysis of
samples from each sand pile revealed that PCB concentrations were 4,600,
3,300, and 88 mg/kg. Following treatment, PCB concentrations had been
reduced to 94, 47, and 4 mg/kg in composite samples.
Another test was conducted on 15m3 (20 yd3) of soil, described as a
sandy loam contaminated with PCBs in concentrations up to 200 mg/kg.
Following treatment, residual PCB concentrations in the treated soil varied
between 2.5 and 4.5 mg/kg. During this test, ambient outside temperatures
ranged from -15° to -12°C (-10° to 5°F). The prototype system was not
insulated and, therefore, suffered heat loss. Terra-Kleen, the system devel-
oper, believes that the temperatures decreased extraction efficiencies sig-
nificantly.
Soil samples contaminated with diesel fuel in concentrations up to 6,190
mg/kg have also been treated. A removal efficiency of 98% was achieved.
4.6
-------
Chapter 5
5
PROCESS EVALUATION
Solvent/chemical extraction (SCE) is effective in separating a wide range
of organic contaminants from soils, sludges, and sediments (see table 4.1 on
page 4.2), thereby reducing the volume of contaminants, which may require
further treatment. In addition, SCE has been demonstrated to be effective in
treating a number of RCRA-listed wastes such as wood treating wastes
(K001), slop oil emulsion solids (K049), American Petroleum Institute
(API) separator sludge (K050), and tank bottoms (K052). The technology
has been applied also in treating drilling muds, coal tar wastes, paint wastes,
synthetic rubber process wastes, pesticide and insecticide wastes, and oth-
ers. It has been selected in six Records of Decision to clean up Superfund
sites (US EPA 1992e).
SCE is evaluated under the following parameters:
• levels of removal of contaminants;
• status of development; and
• costs.
5.1 Levels of Removal of Contaminants
Concentration factors of up to 10,000:1 have been measured. This repre-
sents a significant reduction in the volume of contaminants requiring further
treatment.
Removal efficiencies and levels of reduction that can be effected vary
with the particular process, the number of extraction stages, the type and
concentration of contaminants, and the nature of the medium. Reduction of
>98% of polychlorinated biphenyls (PCBs) at levels up to 4,600 ppm and
reduction of >95% of polyaromatic hydrocarbons (PAHs) at levels up to
2,900 ppm have been reported by the technology vendors. Overall organics
5.1
-------
Process Evaluation
recovery efficiencies of greater than 99% are claimed by one vendor (CF
Systems 1992).
Removal efficiencies >90% are generally reported for all organic con-
taminants with residual levels in many cases <1 ppm. This performance,
however, may require a high number of extraction stages (6 to 8), particu-
larly when there are very high initial concentrations.
5.2 Status of Development
Two systems, CF Systems and Carver-Greenfield, have completed US
EPA Superfund Innovative Technology Evaluation (SITE) demonstration
programs and are fully documented (US EPA 1989; 1992a). One other
system, Best Extractive Sludge Treatment (B.E.S.T.), has undergone a 24-
hour US EPA evaluation program and a report has been issued (US EPA
1988). Three systems (B.E.S.T., Extraksol, and Soil Restoration Unit
(S.R.U.)) are currently in the US EPA SITE Program (US EPA 1992g;
Meckes et al. 1992).
All of the system suppliers are offering commercial systems for a wide
variety of applications. Most applications require treatability testing to
enable site-specific design parameters to be determined. Treatability tests
show considerable variation in results from different sample sources; there-
fore, a well-planned and executed treatability test program is needed to
properly set site-specific design parameters (US EPA 1992b).
5.3 Costs
Unit cost data were solicited from each process vendor and that received
was augmented with other published cost data. See table 5.1 (on page 5.3),
which reports unit costs varying from $105 to $770 per tonne ($95 to $700
per ton). The values presented in table 5.1 are estimates and can vary sub-
stantially depending on the contaminant type and concentration,, the media,
and the quantity of material to be treated. The quoted unit costs include the
cost of disposal and destruction or treatment of all residue, analyses associ-
5.2
-------
Chapter 5
TableS.l
Cost Comparison
Wet vs.
Quoted Costs Dry Site Quantity Disposal/
S/tonne Pricing Preparation Tonne Destruction Mob**/ Profit
Process (S/ton)* Basis Included (Ton) of Residues Analytical Demob Included
B.E.S.T.
CF
Systems
Carver -
Greenfield
Extraksol
LEEP®
NKDa
S.R.U.
165(150)
110-550
(100-500)
129-576
(117-523)
771 (700)
105-330
(95-300)
138-330
(125-300)
220-661
(200-600)
Wet
Wei
Wet
Wet
Wet
Wet
Wet
No
Yes
Yes
No
Yes
No
No
18,000
(20,000)
>57,000
(>63,000)
21,000
(23,000)
910
(1,000)
>40,000
(44,000)
18,000
(20,000)
450 (500)
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Vanes
Yes
No
Varies
Yes
Vanes
Varies
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Unknown
Yes
Yes
Yes
Unknown
Yes
* Costs are estimates only and are expected to be site specific
" Mob = mobilization, demob = demobilization
a - data is for both process variations
ated with system operations (except for Carver-Greenfield), and mobiliza-
tion and demobilization.
The US EPA has published detailed cost estimates for the CF Systems
Process (US EPA 1990a) and the Carver-Greenfield Process (US EPA
1992f). These estimates include technology-specific costs and a breakdown
of site-specific costs. In estimating costs for the CF Systems Process, the
US EPA postulated the following scenarios:
• a base case treating 800,000 tonne (880,000 ton) of sediments
contaminated with PCBs in concentrations of 580 ppm at 450
tonne/day (500 ton/day) over a 3.3-year period; and
• a hot-spot case treating 57,000 tonne (63,000 ton) of sediments
contaminated with PCBs in concentrations of 10,000 ppm at 90
tonne/day (100 ton/day) over a one-year period; and
• analytical costs of $500/day in both of the above cases.
The estimated cost for the base case was $163±20% per tonne ($148
±20% per ton) of raw feed, including excavation and pre- and posttreatment
5.3
-------
Process Evaluation
costs, but excluding final contaminant destruction costs. Excavation and
pre- and posttreatment costs were estimated to be 41% of the total costs.
The estimated cost for the hot-spot case was $492, -30% +50%, per
tonne ($447, -30% +50%, per ton) of raw feed. Excavation and pre- and
posttreatment costs were estimated to be 32% of the total costs (US EPA
1990b).
The EPA's estimate for the Carver-Greenfield Process assumed treat-
ment of 21,000 tonne (23,000 ton) of drilling mud contaminated with petro-
leum wastes. The total cost estimate was $576/wet tonne ($523/wet ton),
with $243/tonne ($221/ton) allocated to technology costs. Site costs were
estimated to be $333/tonne ($302/ton), including $264/tonne ($240/ton) for
incineration of contaminated residuals. The estimate excluded regulatory,
permitting, and analytical costs because of their variability. Excluded also
were effluent treatment and disposal costs. Rather than assuming a cost for
incineration, the vendor assumed that the process would separate indig-
enous oil, which would be sold to a refinery for $26/tonne ($24/ton), result-
ing in an overall cost of $285/tonne ($259/ton) (US EPA 1992g).
An estimate of the NKD Process treatment costs for the cleanup of a
15,300 m3 (20,000 yd3) site is in the $164 to $327/m3 ($ 125 - $250/yd3)
range (Massey and Darian 1989). These costs were based on battery limits
operation of a mobile system with net daily throughput rates in the range of
96 to 191 m-Vday (125 to 250 ydVday). An on-stream factor of 85% was
assumed. The estimate included allowances for capital and operating ex-
penses, waste disposal, mobilization, and demobilization.
For the treatment of refinery sludges, NKD originally set a treatment cost
target of $330/tonne ($300/ton) of raw sludge. With a pilot study nearly
complete, Massey and Darian (1990) reported that this target was still con-
sidered to be achievable. The estimate included allocations for pretreat-
ment, amortization of capital, maintenance, manpower, chemicals, utilities,
stabilization of solids, disposal of stabilized solids, and credit for recovered
oil.
As the above discussion shows, costs for SCE can vary significantly
depending upon the particular site. Treatability and site-specific cost stud-
ies are required to prepare meaningful cost estimates. The costs reported,
however variable, appear competitive with costs for alternative remedial
technologies.
5.4
-------
Chapter 6
6
LIMITATIONS
6.1 Site/Matrix Considerations
Solvent/chemical extraction (SCE) processes are designed to remove and
concentrate organic contaminants from soils, sludges, sediments, and waste-
waters. Currently, they are not normally effective in removing inorganic
contaminants, such as heavy metals. Although SCE processes have been
demonstrated to be highly effective in the removal of polychlorinated bi-
phenyls (PCBs) and polyaromatic hydrocarbons (PAHs), they may be less
effective in treating organic compounds that are highly hydrophilic and of
high molecular weight. The processes are not designed to treat particular
compounds, and extraction efficiencies and processing rates are lower when
there are high concentrations of indigenous organic compounds in the feed
material. Similarly, extraction efficiencies and processing rates are lower
when emulsifiers and water-soluble detergents are in the feed (US EPA
1991c).
Water was found to be a major impediment to effective operation of the
NuKEM Development (NKD) soils remediation process. Early investiga-
tions revealed that as little as 10% moisture in the soil could significantly
hinder extraction of PCBs. To overcome this problem, NKD has added a
proprietary reagent (Massey and Darian 1989).
All of the SCE processes evaluated require some level of feed prepara-
tion before the extraction operation. Crushing and/or screening is required
to reduce feed material to a maximum size of between 6 and 76 mm (0.25
and 3 in.). Most processes are limited to a well-delineated range of feed
solids contents. This may necessitate a dewatering and drying stage in
some processes and a slurrying stage in others. The Basic Extractive
6.1
-------
Limitations
Sludge Treatment (B.E.S.T.) Process may require pH adjustment to between
10.5 and 11, and the CF Systems Process, to between 6 and 10.
All of the processes addressed in this monograph have undergone sub-
stantial process development, testing, and evaluation. These evaluations
have produced mixed results, often due to site-specific matrix consider-
ations. In a number of cases, test objectives have been met or exceeded,
while in other cases they have not been achieved. This reinforces the need
for site-specific treatability testing and/or a detailed review of past test re-
sults.
6.2 Residue Treatment
The cleaned solids fraction may, in some cases, be deemed a Resource
Conservation and Recovery Act (RCRA) hazardous waste, requiring stabili-
zation or other treatment before disposal (see Section 3.7).
The SCE process can remove all indigenous organics and kill beneficial
microbes in the feed material. If the residual solids are to be used as top
soil, soil amendments will be required.
The concentrated contaminants fraction may often require additional
treatment to ensure destruction of toxic organic compounds or to prepare
this fraction for recycling (see Section 3.6). If organometallic compounds
are present in the feed, they may be coextracted and concentrated in this
fraction, thus further complicating final treatment. In some applications,
however, this fraction may contain only petroleum hydrocarbons and, there-
fore, may be suitable for recycling as is.
The wastewater stream must be treated before being discharged to a wa-
ter course and may require treatment before being discharged to a publicly
owned treatment works (POTW) (see Section 3.7).
The extraction fluids can become contaminated with refractory com-
pounds and require either a bleed stream or periodic replacement within the
process. This results in another waste stream, which may require additional
treatment before recycling or disposal.
6.2
-------
Chapter 6
6.3 Process Risks
All of the SCE processes use flammable organic extraction fluids pre-
senting potential fire and explosion hazards. The flammability of these
extraction fluids varies greatly. The CF Systems Process uses light pressur-
ized hydrocarbons, presenting the greatest potential risk of explosion. Sev-
eral of the extraction fluids include volatile or semivolatile compounds,
which can create explosive vapor mixtures.
A number of the extraction fluids include toxic organic compounds, and
therefore are subject to regulations governing the storage, use, transporta-
tion, and disposal of hazardous wastes. Process designs must minimize or
eliminate personnel exposure to these compounds.
6.4 Reliability
SCE has only recently been applied in the remediation of contaminated
soils, therefore, little data on commercial plant operations are available to
evaluate long term reliability. Most data come from bench-scale, pilot-
scale, or demonstration plants. U.S. Environmental Protection Agency
Superfund Innovative Technology Evaluation (SITE) demonstration reports
(US EPA 1990e; 1992a) for CF Systems and Carver-Greenfield identified
some operating problems, including foaming of the extraction fluids, gum-
ming-up of process lines, and intermittent sticking of solids to process
equipment. Corrective actions have been identified, which, it is believed,
will solve these problems in full-scale applications.
Although treatability tests at the bench scale have shown that SCE is
applicable to a wide range of contaminants, they have shown also that pro-
cess parameters must be optimized for each application.
More commercial applications treating run-of-site feed are needed to
demonstrate whether SCE processes can handle the variations in feed prop-
erties that can be expected. Until these data are available, extensive site-
specific treatability testing should be considered when applying this
technology.
6.3
-------
-------
Chapter 7
•7
TECHNOLOGY PROGNOSIS
The use of solvent/chemical extraction (SCE) for the treatment of con-
taminated soils, sludges, sediments, and wastewaters represents new appli-
cations of a widely-used and well-understood technology. SCE is used in
varied industries such as foods, pharmaceuticals, fire chemicals, mining,
and minerals processing. The unit operations involved are simple and well
understood.
Although the unit operations are well proven in other applications, their
use for soil cleanup is still in its infancy. Most of the processes discussed in
this monograph have few full-scale commercial applications. While it is
expected that this will change in the future, SCE is a developing treatment
technology requiring site-specific application testing and evaluation.
SCE has demonstrated a number of advantages in other industries. It is
expected that these advantages will also apply to its use in treating soils,
sludges, sediments, and wastewaters. These advantages include:
• Demonstrated high removal efficiencies and low residual values
for a wide range of organic contaminants (polychlorinated bi-
phenyls (PCBs), polyaromatic hydrocarbons (PAHs), petroleum
hydrocarbons, pesticides, and dioxins);
• Demonstrated high concentration factors (up to 10,000:1), re-
sulting in greatly reduced volumes of material requiring addi-
tional treatment; and
• The concentrated contaminant streams, especially when petro-
leum hydrocarbons are the soil contaminant, have the potential
for recycle.
7.1
-------
Technology Prognosis
Although SCE has had limited application to date, there are indications
pointing to its likely expanded application in site remediation, including the
following:
• Several SCE processes are under, or have completed, evaluation
in the U.S. Environmental Protection Agency's (US EPA's)
Superfund Innovative Technology Evaluation (SITE) demon-
stration program, which provides independent verification of the
processes' efficiency, operability, and cost;
• Commercial SCE processes are already being used to treat petro-
leum refinery and other waste streams, allowing determination
of long-term costs and system reliability;
• The SCE processes do not require extensive pretreatment of the
feed (other than size reduction) and can tolerate a wide .range of
soil moisture content (from about 5% to 90% moisture): and
• The SCE processes are cost-competitive with other technologies
used to treat organic-contaminated soils, sludges, and sediments.
Several companies are working on developing proprietary SCE processes
that will expand options for applying SCE (see Appendix B for discussions
of some emerging processes). Further, as additional systems are brought on
line, process uncertainties may be minimized and treatment costs should
decrease.
7.2
-------
Appendix A
VENDOR CONTACTS
B.E.S.T.
Resource Conservation Corporation
3006 Northrup Way
Bellevue, Washington 98004-1407
Phone: (206)828-2400
LEEP
ART International, Inc.
100 Ford Road
Denville, New Jersey 07831
Phone: (201)627-7601
CF Systems
Morris Knudsen Company
3D Gill Street
Woburn, Massachusetts 01801
Phone: (617)937-0800
NKD Process
NuKEM Development
3000 Richmond Avenue
Houston, Texas 77479
Phone: (713)520-9994
CF Technologies
1 Westinghouse Plaza, Suite 200
Hyde Park, Massachusetts 02136-2059
Phone: (617)364-2500
SRU
Terra-Kleen Corporation
7321 North Hammond Avenue
Oklahoma City, Oklahoma 73132
Phone: (405)728-0001
Carver-Greenfield Technology Contex Process
Dehydro-Tech Corporation
6 Great Meadow Lane
East Hanover, New Jersey 07936
Phone: (201)887-2548
A/S Phoenix Milj0
Vester Alle 1
6600 Vejen, Denmark
Phone: (45-75)361-111
A.I
-------
Vendor Contacts
Extraksol Process LIX Process
CET-Sanivan Henkel Corporation
7777 Boulevard L.H. Lafontaine 2330 Circadian Way
Anjou, Quebec HIK 4E4, Canada Santa Rosa, California 95407
Phone: (514)355-3351 Phone: (707)576-6227
RIP/CIP Process
Davy Research & Development
P. O. Box 37
Bowesfield Lane
Stockton-on-Tees, Cleveland TS18 3HA
England
Phone: (44-642)607-108
A.2
-------
Appendix B
B
EMERGING PROCESSES
In addition to the processes addressed in the monograph proper, several
other processes that show promise for expanding the use of solvent/chemi-
cal extraction (SCE) in site remediation are being developed. Five pro-
cesses, demonstrated at the bench scale, were deemed to merit review here
(see table B.I on page B.2). Two of them, the Liquid Ion Exchange (LIX)
and Resin-in-Pulp/Carbon-in-Pulp (RIP/CIP) Processes, incorporate tradi-
tional mining and minerals processing concepts in separating inorganic, as
well as organic, contaminants from soils. One of the processes, Contex, has
been employed commercially in Denmark and is currently undergoing ma-
jor modifications to improve throughput. The Adiabatic Process for the
Extraction of Sludges and Soilex Process have been successfully tested at
the bench scale, but further development has not been undertaken.
Chemical Waste Management Adiabatic Process for the Extraction of
Sludges. In the late 1980's, Chemical Waste Management began develop-
ing the Adiabatic Process for the Extraction of Sludges, at times called the
APES, for removing water and organics from sludges (Henry and
Gillenwater 1992). Bench-scale studies were carried out, and construction
of a pilot plant was begun. These efforts were discontinued in 1991.
Figure B.I (on page B.3) is a flow schematic for a scenario in which a
sludge containing solids, water, and relatively volatile organics is to be
treated with the objective of producing dry, organic-free solids and recover-
ing at least part of the organic contaminants. The process is to be fully
continuous. In the evaporation step, sludge is fed into a forced circulation
evaporator in which a heavy, "nonvolatile" oil is circulated. When the
heavy oil and sludge contact moisture, volatile organic compounds and
semivolatile organic compounds are evaporated. These vapors are sent
forward to a catalytic oxidation system in which the organic compounds are
destroyed. The catalytic oxidation step is not required for sludges that do
not contain volatile organics.
B.I
-------
Emerging Processes
Table B.I
Bench Scale & Promising SCE Processes
Technology
Name
APES
Developer
Chemical
Waste
Management
Level of Development
Bench scale.
Pilot plant constructed.
Targeted Applications
Organic contaminanl removal from
sewage, millscale, and petroleum
sludges. Not currently marketed.
Contex
LIX
Phoenix Milj0
Henkel
Full-scale fixed facility, 9
tonne/hr(10ton/hr).
Process undergoing major
modification.
Restart Dec. 1992
Methylene chloride solvent.
Bench scale.
Utilizing traditional mining SX
processes.
Organic contaminated soils. +99%
removal of BTX, naphthalene,
phenanthrene, and chlorinated
solvents reported
Heavy metals (Cd, Cu, Ni, Pb, Zn)
removal from soils
RIP/CIP
Soilex
Davy
Research &
Development
Martin
Marietta
Bench scale.
EPA SITE program
Traditional mining processes
Bench scale and batch pilot
tests, 1984, DOE Oak Ridge,
Tennessee.
Inorganic contaminant removal
using resm-m-pulp (RIP)
technology. Organic contaminant
removal using carbon-i n-pulp (CIP)
technology.
PCB removal from soils. +90%
removal reported Not currently
marketed.
A second stream leaving the evaporator is composed of solids, the heavy
oil utilized in the evaporator, and any low-volatility oils in the original
sludge feed. In the extraction step, a volatile alkane solvent is used to sepa-
rate the oils from the solids in a continuous countercurrent multistage op-
eration.
The extract, which contains the light solvent and the oils, is then frac-
tionated to recover the solvent; the solvent is recycled. The bulk of the oil
is recycled to the evaporator. Any excess beyond that needed to maintain
the inventory in the evaporator is disposed of.
The solvent-laden solids from the extraction step are sent to a dryer.
This is the solids desolventization phase, part of the product preparation
step. Solvent volatilized in the dryer is recycled, and the dry, oil-free solids
are discharged.
B.2
-------
Appendix B
Figure B. 1
Chemical Waste Management APES Flow Schematic
Intended applications included treating municipal sewage sludge, mill-
scale sludge, and petroleum refinery sludges (Resource Conservation and
Recovery Act (RCRA) waste codes K048 through K052).
Phoenix Milj0 Contex Process. Phoenix Milj0 (Environmental) of
Vejen, Denmark (Phoenix), has developed and operated a semimobile SCE
process for the treatment of contaminated soils from industrial sites and
drilling operations (N0rregaard 1992). In 1990, Phoenix built and began
operating a nominal 9-tonne/hr (10 ton/hr) demonstration plant at its facili-
ties and has tested between 20 to 30 different soils contaminated with tar,
petroleum hydrocarbons, drilling cuttings, chlorinated solvents, benzene,
toluene, xylene (BTX) compounds, naphthalene, and phenanthrene. The
vendor claims very high removal efficiencies and low residual soil organics
in their brochure (Phoenix 1991).
B.3
-------
Emerging Processes
Liquid-solid extraction is combined with steam stripping in a process
whose operating parameters can be adjusted to achieve required removal
efficiency for each application (see figure B.2 on page B.4). Contaminated
soil is fed through an inlet seal leg into a series of screw conveyors. The
extraction fluid, methylene chloride, is fed countercurrent to the soil.
The first conveyor serves as the extraction stage. The second conveyor
serves as a drainage device to remove extraction fluid from the soil. The
soil then enters a steam-stripping unit, where residual extraction liquid is
removed. The decontaminated soil leaves the extraction system via an out-
let lock.
The extraction liquid containing the organic contaminants is condensed
and transferred to the extraction conveyor. Makeup lean extraction fluid
from a buffer tank is added at this point. The loaded extraction liquid flows
from the extraction conveyor to a distillation unit, where it is separated for
Contaminated
soil
Figure B.2
Phoenix Contex Process
Condensation
o
WClosed loop
ith extraction
liquid
Decontaminated
soil
Buffer tank
extraction
liquid
Concentrated
Contaminants
B.4
-------
Appendix B
recycle. The concentrated contaminant stream is collected for transport to
an off-site facility for further treatment.
Phoenix is currently performing major modifications to its on-site pro-
cessing plant. The goals of these modifications are to improve system reli-
ability and increase plant capacity for a wider range of soils. Previous
experience has been that clay-containing soils cause handling problems and
reduce plant capacity. The modifications were scheduled to be completed
in mid-1993, at which time characterization testing will resume.
The developer indicates very favorable economics for the Contex pro-
cess. A very rough estimate of the capital costs for the demonstration plant
is between $2,000,000 and $2,300,000. Treatment costs of $110 to
$193/tonne ($100 to $175/ton) were quoted. Significant feed properties that
influence treatment costs are soil water and oil content, as well as soil type
(N0rregaard 1992).
Henkel Liquid Ion Exchange Process. Henkel Corporation is a major
producer of liquid ion exchange reagents for the mining and minerals pro-
cessing industry. These reagents are widely used to extract metals, such as
copper, nickel, uranium, and zinc, from leaching solutions having great
specificity for metals of interest in liquids that contain high concentrations
of several competing compounds.
Henkel's Hazardous Waste Division has performed a series of bench-
scale treatability studies of soils contaminated with heavy metals (Virnig
1992). To date, the work has concentrated on the removal of lead from
soils. Additional work is planned on developing process concepts and test-
ing Liquid Ion Exchange reagents for the removal of cadmium, copper,
nickel, and zinc from contaminated soils.
Successful demonstration of the Henkel LIX processes may lead to a
much wider application of SCE in the treatment of contaminated soils.
Davy R&D Resin-in-Pulp/Carbon-in-Pulp Process. Davy International's
Research and Development Division (Davy R&D) in Stockton, England, is
developing an RIP/CIP Process for the treatment of contaminated soils.
The RIP/CIP technology is used in the mining and minerals processing
industry to concentrate valuable metals from slurried ore bodies and their
leachates. The RIP/CIP Process is suitable for the treatment of a wide range
of materials contaminated with both inorganic and organic wastes (US EPA
1992e).
B.5
-------
Emerging Processes
Figure B.3
Davy R&D RIP/CIP Process
Soil
,-, X
1 Tramp ^_ S _ Tramp
1 disposal ^^ removal
"---' S n^ r-
1 |
' rrmh , v Wet F Leat.h S/L Sl7
' i * screcn ^ ,,
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1
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^ ^ wash
F = Fine S | S ^.
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^
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U
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S/L L
V >
Free
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L = Lqu,d T C°"Ce
R = Resin/Carbon Decontaminated comalr
= Alternatives soil
h
en
f
ip./
tie
itratee
inant
The process (see figure B.3 on page B.6) entails leaching of organic and
heavy metals from contaminated soils followed by the adsorbing and re-
moving of contaminants by activated carbon or ion exchange resins. The
RIP ion exchange processes are most appropriate for metal removal,
whereas the CIP adsorption processes are more suitable for the removal of
organic contaminants.
Contaminated material is passed through screening stages in order to
separate tramp and oversize material. In the case of metal contamination,
the oversize material could be crushed or undergo a vat leach before wash-
ing and disposal. The soil then passes to stirred vessel leaching stages. The
leached pulp is physically separated into a sand fraction and a slime frac-
tion. The sand fraction wash liquor (the leachate), and the slime fraction
(the pulp) contain the bulk of the contaminants. The pulp is passed to a
multistage RIP contactor, where the contaminants are removed by ion ex-
change resin. The resin is stripped to remove the contaminants and then
B.6
-------
Appendix B
recycled back to the RIP contactor. The concentrated contaminants present
in the strip solution are precipitated as a concentrated sludge for recycling
or disposal.
A similar process will be used in removing organic contaminants, with
appropriate aqueous reagents and surfactants used as leaching agents. The
activated carbon will cause the contaminants to be desorbed chemically or
thermally, and the carbon will be reactivated for reuse in the CIP process.
Desorption products can be disposed of or recycled.
The technology was accepted in the Superfund Innovative Technology
Evaluation (SITE) Emerging Technology Program in July 1991, and labora-
tory bench-scale tests have been underway since (US EPA 1992e). Initial
efforts focused on remediation of soil contaminated with arsenic, copper,
and chromium. These tests have shown removal efficiencies of over 90%.
More recent tests have concentrated on removing mercury from contami-
nated soils.
Process data from the above tests are being used to prepare conceptual
cost estimates (± 30%) for a nominal 140-tonne/day (150 ton/day) plant.
Locations were being screened for operation of a 1.8-tonne/day (2 ton/day)
pilot plant beginning sometime in 1993. Process data are being developed
for treating soils containing both metals and organic contaminants (Naden
1992).
Martin Marietta Soilex Process. Martin Marietta Energy Systems, Inc.,
(MMES) conducted bench- and pilot-scale studies of extraction of poly-
chlorinated biphenyls (PCBs) from soil in 1984 using their Soilex Process
(Napier, Hancher, and Saunders 1990; Hancher, Napier, and Kosinski
1984), but no attempt to commercialize the technology has been made or is
planned. The studies were performed at the U.S. Department of Energy Y-
12 Plant in Oak Ridge, Tennessee, on soil containing PCBs in concentra-
tions of 300 to 600 ppm.
In the process shown in figure B.4 (on page B.8), feed was reduced in
size and screened so that most soil particles were less than 6 mm (.25 in.) in
diameter. The screened soil was then washed with a mixture of 50% water
and 50% kerosene by volume. The PCBs and oil were extracted into the
water/kerosene phase, the soil was dried and chemically analyzed, and the
extent of PCB removals was determined.
B.7
-------
Emerging Processes
The water and kerosene mixture was allowed to separate in phase, and
the water was returned to the process. The kerosene extract was distilled to
obtain purified kerosene, which was returned to the process, and a PCB/oil-
contaminated phase. The kerosene used in these studies had a boiling point
of 180° to 210°C (356° to 410°F), a flash point of 50°C (122°F), and an auto-
ignition temperature of 360°C (680°F).
Before the pilot-scale studies, a number of laboratory shakedown tests
were conducted to define the best water-kerosene-soil ratios. Satisfactory
Figure B.4
Martin Marietta Soilex Flow Schematic
Treated
soil & water
Decontaminated
soil
B.8
-------
Appendix B
results were obtained using equal volumes of water and kerosene plus 10%
soil by weight. In one test, soil containing a concentration of 600 ppm
PCBs underwent three extractions and the concentration was reduced to 13
ppm, an overall reduction of 97.8%. The rate of removal was nominally
70% per stage.
The three-stage countercurrent extraction pilot-plant operation was a
batch process with each stage requiring a nominal 24 hours for mixing and
settling. Each extraction stage employed a 200-L (55 gal) drum equipped
with an agitator to stir the soil, water, and kerosene mixture. The soil and
water were added in the first stage, and clean kerosene was added in the
third stage. Either 15 or 24 kg (33 or 53 Ib) of contaminated soil was added
in the first stage, which contained 76 L (20 gal) of water and 76 L (20 gal)
of kerosene from the second stage. The mixture was stirred for about 30
minutes and then allowed to settle for 16 hours. The treated soil was then
sent to the second stage, etc. The three extraction stages required three days
to complete, but once the stages were filled, a batch was added and taken
from the process daily.
Seventeen runs were made in the pilot plant, and the three extraction
stages removed an average of 91.6% of PCBs over a removal range of
85.3% to 97.9%. The results indicate that each additional stage would have
removed about 70% of the remaining PCBs. Two tests reduced the PCBs
from starting concentrations of 280 and 340 ppm to 6 ppm. After three
stages, the PCB range of the treated soil from all of the pilot-plant tests was
6 to 50 ppm, in soil contaminated initially with 240 to 360 ppm PCBs.
The kerosene phase (extract) from the first stage was distilled to obtain a
concentrated PCB-kerosene phase and a recyclable kerosene containing
practically no PCBs. In laboratory tests, 87.5% of the kerosene could be
vacuum distilled and used in the recycle operation. The pilot-plant distilla-
tion was carried out in a steam-heated still that could not be operated in a
vacuum mode. Because of the low-pressure steam used in the plant, a
maximum temperature of 150°C (302°F) was applied, allowing recovery of
only 82% of the kerosene. Higher distillation temperatures would have
allowed more kerosene to be recycled, reducing the amount of PCB-kero-
sene left for disposal by incineration.
The water/kerosene phase separated during the soil settling period. The
kerosene was transferred to the next extraction stage or to the distillation
process. The water phase was separated from the spil after the third extrac-
B.9
-------
Emerging Processes
tion stage through a settling stage, and the water was returned to the first
stage without purification. The water was used to reduce the amount of
kerosene required and to serve as a fluid to transfer the soil from one wash
station to the next.
The soil was wet with water and kerosene after the third stage. The pi-
lot-plant tests did not remove either the water or the kerosene, but they
would have been removed through heating the soil and condensing the liq-
uids if the process had been further developed.
Pilot-scale tests were conducted of a process to extract PCBs from oil
employing a continuous countercurrent extraction column and using dim-
ethyl formamide as the solvent. After extraction, water was added to the
dimethyl formamide and PCB extract, causing a phase separation with one
phase containing the PCBs and the other, the dimethyl formamide and wa-
ter. The latter mixture was then separated by distillation, and both products
were recycled through the process. As with the PCB-in-soil process, no
attempt has been made to commercialize this technology. (Hancher,
Napier, and Kosinski 1984.)
B.10
-------
Appendix C
C
CARVER-GREENFIELD PROCESS
Results of four studies of the Carver-Greenfield Process treating a vari-
ety of contaminated materials are reported below. The pilot-scale data in
case study #1 were provided in the report of an U.S. Environmental Protec-
tion Agency (US EPA) Superfund Innovative Technology Evaluation
(SITE) demonstration. The remaining studies were conducted by Dehydro-
Tech Corporation (DTC) and were not available for review.
CASE STUDY #1: LABORATORY TESTS AND US EPA SITE PILOT-
SCALE DEMONSTRATION AT PAB OIL
The US EPA SITE demonstration was conducted in August, 1991 using
drilling mud waste from the PAB Oil and Chemical Services (PAB Oil)
Superfund Site in Abbeville, Louisiana (US EPA 1992a). Drilling mud
wastes consist of oil, solids, and water that become mixed during the pro-
duction of oil (US EPA 1992a). As reported by the developer, initial labo-
ratory-scale tests showed the wastes consisted of 29.5% solids, 29.1%
water, and 41.4% oil (Trowbridge, Holcombe, and Kollitides 1991). The
laboratory tests reduced toluene content from 18,600 ppb to less than 350
ppb, while acetone, ethylbenzene, and xylenes, which had been present in
the feed in concentrations of from 2,000 to 10,000 ppb, were undetectable
in the treated solids (Environment Today 1992).
Following the laboratory tests, a 44-kg/hr (100 Ib/hr) pilot-scale system
was used in the 1991 SITE demonstration to assess how effectively the
process separated petroleum-based, hydrocarbon-contaminated drilling mud
wastes into their solid, oil, and water fractions. The study included shake-
down runs (to optimize operating conditions), a blank run (with no waste
treatment), and two test runs. The following information is based primarily
on the US EPA Aug. 1992 Applications Analysis Report (US EPA 1992a).
Isopar-L was used as the extraction solvent, and the waste was screened
to 0.64 cm (0.25 inch) before processing. The raw feed and solids product
C.I
-------
Carver-Greenfield Process
were analyzed for solids/indigenous oil/water (SOW) content. Although the
raw feed contained significant levels of indigenous oil and elevated levels
of metals (US EPA 1992a), the feed, as well as the treated solids, passed
toxicity characteristic leaching procedure (TCLP) tests.
During shakedown testing treating silt, a gummy material formed, plug-
ging process lines. In the next shakedown, a surfactant was used with the
silt to prevent formation of the gummy substance. The final product, how-
ever, was found to contain 4% indigenous oil, while the clean silt contained
no indigenous oil. The report concluded that the surfactant had been de-
tected as indigenous oil in the SOW analysis, and its use was, therefore,
discontinued (US EPA 1992a).
A blank run was then conducted using bentonite as the solid matrix, and
no surfactant was added. Once again, lines became blocked with gummy
material, and this initial blank run was discontinued. It should be rioted that
different materials were used in the shakedown and blank runs; therefore,
consistent process adjustments could not be made.
Following these runs, the SITE demonstration was started. A blank run
using bentonite was conducted, and waste feed processing began. Two
waste feed test runs, each consisting of three extractions, were conducted.
The system was operated in a batch mode using fresh solvent for each ex-
traction, because of the pilot-scale nature of the test (US EPA 1992a).
Samples of waste feed, raw solvent, slurried feedstock, concentrate: (from
each extraction), centrifuge cake, condensed water, condensed solvent,
solids product, and vent gas were collected. The condensed water and con-
densed solvent resulted from materials collected from evaporation during
the extraction steps that were condensed and then manually separated using
a separatory funnel. The vent gases were those that had not been con-
densed, and were passed through a granular-activated carbon canister (US
EPA 1992d).
Approximately 136 kg (300 Ib) of feed was fluidized in 680 kg (1,500 Ib)
of solvent (Trowbridge 1992). As the developer explained, the extraction
temperature of 66° to 93°C (150° to 200°F), was maintained for 15 minutes
to one hour. In one of the extractions, the mixture was heated to a higher
temperature (around 107° to 135°C (225° to 275°F)) to evaporate the water
from the feed. After centrifuging, the solvent was vaporized from the solids
using inert gas at 177°C (350°F) (Trowbridge, Holcombe, and Kollitides
1991).
C.2
-------
Appendix C
The analytical results of the tests are presented in table C.I (on page
C.4). Each feedstock contained approximately 52% solids, but the indig-
enous oil content differed (feedstock 1 was =17% oil, and feedstock 2 was
=7% oil). Based on summaries of the SITE demonstration (US EPA 1992f;
US EPA 1992a), the final solids product contained approximately 0.9%
carrier oil (0.93% for test 1, and 0.89% for test 2) and approximately 0.9 to
1.5% indigenous oil (1.38 to 1.45% for test 1 and 0.85% for test 2).
The method of determining oil removal made it difficult to characterize
test results. The Isopar-L solvent is detected through total petroleum hydro-
carbon (TPH) analysis. Consequently, the SITE demonstration data was
based on concentrations calculated by subtracting Isopar-L levels (based on
gas chromatography to determine the Isopar-L levels). The following tests
were used to gather data on oil:
• Solids/Indigenous Oil/Water Content. The indigenous oil de-
tected through this analysis includes a broad range of polar and
nonpolar organics that are soluble in toluene, including petro-
leum hydrocarbons. Polar organics or surfactants may be de-
tected as oil in the SOW procedure;
• Total Petroleum Hydrocarbon. The TPH analysis uses silica gel,
which contains polar organics and surfactants (Trowbridge
1992). As a result, the TPH analyses detected only nonpolar
organics, including the Isopar-L solvent; and
• Solvent Levels. The Isopar-L solvent levels were characterized
through gas chromatography.
The SITE demonstration calculated "indigenous TPH" by subtracting the
Isopar-L result from the TPH result. This calculation was then used to de-
termine removal efficiencies. Several important qualifications are intro-
duced by the SITE demonstration method of calculating removals. First,
the resulting calculations sometimes resulted in negative concentrations (the
Isopar-L gas chromatographic results were higher than the total TPH levels,
resulting in a negative calculation for the indigenous TPH). The indigenous
TPH was therefore reported as 0 in the final product, resulting in calcula-
tions of 100% removal (see table C.2 on page C.6). This approach may be
flawed, however, since it is based on the assumption that the obvious dis-
crepancies in the analyses (perhaps due to nonhomogenous sample results,
analytical difficulties in quantifying exact levels, or other factors) act solely
C.3
-------
Carver-Greenfield Process
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C.5
-------
Carver-Greenfield Process
Table C.2
Carver-Greenfield Site Demonstration: Oil Parameters
Test Run #1
Test Run #2
Parameters
Feedstock Final Solids
Feedstock Final Solids
SOW1
- Solids 5
- Indigenous Oil
- Water
TPH1
-TPH
Isopar - L1
- as solvent 0
-as TPH 0
Calculated Oil1
- indigenous oil
- indigenous TPH
- non-TPH oil
Oil Removal Efficiency1
- true indigenous oil
- indigenous TPH
Oil Removal Efficiency2
-oil
2.35
17.48
21.75
14.7
0.93
0.84
1747
14.7
2.77
96.56
1.38
0
0.79
1.38
0
1.38
52.44
7.24
34.7
8.9
0.99
089
7.24
89
98.31
0.85
0
0.66
0.85
0
0.85
(% removal) (% removal)
92.1 883
100 100
(% removal) (% removal)
95.9 94.3
1. Source: US EPA 1992a, C-11
2. Source. US EPA 1992f. These % removals were reported in a SITE demonstration bulletin, basad on the
solids fraction of the influent feed. The bulletin, which summarized results of the SITE demonstration (US
EPA 1992a), reported test run #1 indigenous oil of 1.45% (instead of 1 38%) and carrier oil of 0.03%. Test
run #2 indigenous oil results (0 85%) matched reference 19, and carrier oil was noted to be 0.89%.
in favor of assuming 100 percent removal, without quantifying a potential
range. Second, simply subtracting the Isopar-L solvent levels from the TPH
analysis results ignores the fact that TPH analysis may itself be important
(for regulatory purposes) in determining whether a product is clean. There-
fore, the actual TPH rather than the calculated indigenous TPH may be a
more important factor in evaluating whether the process can be considered
to have successfully treated a material (the fact that the final solids contain
Isopar-L, which is detected as TPH, must be considered).
C.6
-------
Appendix C
As explained in the SITE demonstration report (US EPA 1992a), the
SITE approach qualitatively (rather than quantitatively) characterizes oil
removal, based on a treatment objective of removing indigenous oil.
A review of table C.I (on page C.4) reveals that TPH removals (based on
total TPH, not indigenous TPH) were 94.6% for test run 1 (146,833 reduced
to 7,907 (Og/g) and 92.6% for test run 2 (89,383 reduced to 6,617 |0g/g). As
described earlier, indigenous TPH removals were calculated to be 100%.
Oil removals based on the solids fraction of the influent feed were = 94 to
96% (US EPA 1992g), but indigenous oil removals were = 88 to 92% (US
EPA 1992d).
A gross mass balance (of solids, water, and oil) showed overall recover-
ies of about 96% for both runs. Specifically, test run 1 showed recoveries
of 81.2% of solids, 112.2% of water, and 97.3% of oil; and test run 2,
78.9% of solids, 95.8% of water, and 98.3% of oil (US EPA 1992a).
The following conclusions were stated:
• The Carver-Greenfield Process removed approximately 90% of
the indigenous oil and reduced indigenous TPH to trace levels
on the solids product (US EPA 1992a);
• The solids product consists of a dry powder, similar to dry ben-
tonite with residual oil, attributed primarily to the Isopar-L sol-
vent (a food grade oil) (US EPA 1992a). It should be noted that
other US EPA documents reported approximately equal final
levels of indigenous oil and carrier oil (test run 2, 0.85% and
0.89%), or even higher indigenous oil levels than carrier oil
levels (test run 1, 1.45% and 0.93%) (US EPA 1992g);
• Metals and organics met TCLP criteria, but wastes may, none-
theless, have to be disposed of as hazardous materials because of
regulatory requirements;
• The process does not remove metals bound to the solids and may
increase the apparent metals concentration in the solids because
of volume reduction (US EPA 1992d). Because of this effect, as
table C. 1 (on page C.4 - C.6) shows, the metals concentrations in
the final product solids were consistently higher (on a |Jg/g ba-
sis) than those in the influent feed, except for boron, potassium,
and zinc (test run 1) and boron and vanadium (test run 2). Most
of the reported metal concentrations, however, were below de-
C.7
-------
Carver-Greenfield Process
tection limits. In addition, the US EPA noted that increases in
TCLP extracts could be expected because of the proportional
increase in the amount of solids in the final product, although
there was no evidence that the process increased the actual
leachability of metals (US EPA 1992a); and
• The effluent water requires further treatment because of the
presence of light organics and solvent, but may in some in-
stances be discharged to a local publicly owned treatment works
(POTW) (US EPA 1992a).
The average TPH, based on two test runs, each of which was treated with
three extractions, was reduced from 11.8% in the feed to 0,8% in the final
solids (Holcombe, Trowbridge, and Rawlinson 1991). See table C.3.
Table C.4 (on page C.9) presents a summary of the cost analysis in this
case study. The difference between the US EPA estimate ($244.00/tonne
($221.42/ton)) and the vendor estimate ($122.38 to 238.68/tonne ($111.05
to $216.59/ton)) for the technology-specific cost elements is due primarily
to different assumptions about the amount of labor required. Data from
commercial-scale operations should dispell the disparity.
Table C.3
Carver-Greenfield Site Demonstration: Average
Compositions By Weight Percent
Component
Solids
Water
"Food-Grade" Solvent
Other (non-volatile
toluene extractables)
Total
TPH
Feedstock
52.4
28.2
0.0
12.4
930
11.8
Treated
Sohds
974
<0.1
1.0
1.1
996
0.8
Reprinted by permission of Theodore D Trowbridge from "The Carver-Greenfield Process for the Treatment of
Oily Refinery - • - • - _.__.. . _. . ..
at the Third /
Disposal of f
Trowbridge.
C.8
-------
Appendix C
Table C.4
Carver-Greenfield Cost Analysis Summary
EPA Estimates'
Cost Category (Site Demo)
Technology-Specific
Equipment
Start-up and Fixed
Labor
Supplies (Isopar-L solvent)
Consumables
Facility Maintenance
Demobilization
Technology-Specific Subtotal
Site-Specific
Site Preparation/Excavation
Residuals Treatment
Site-Specific Subtotal
TOTAL
$21.85
4.47
16327
890
15.36
479
278
$22142
55.00
247.02
$302.02
$523 44
Vendor Estimates'
(Site Demo)
$16.16 to $30 18
5.48
59 05 to 147.62
890
1531
3.41 to 6 36
2.74
$11 1.05 to $216 59
30.22 to 53 96
-23.90 to +7 30
$6.32 to $61 26
$117 37 to $246 65
1. Per wet ton of drilling mud waste (31% water. 17% oil, 52% solids) treated, assuming treatment of 23,000
tons of waste
US EPA 1992a
The large difference between the US EPA's and vendor's estimates of
site-specific costs is attributable to different assumptions as to the disposi-
tion of residues. The US EPA posits a cost for treating residue, whereas the
vendor assumes significant recovery and reuse of the residues, thereby off-
setting disposal costs. The capability for recovery and reuse or residue
treatment is highly dependent upon the particular site.
CASE STUDY #2: REFINERY SLOP OIL SAMPLES
Slop oils containing hazardous compounds such as benzene, toluene, and
chromium, were treated in the Carver-Greenfield pilot plant in 1985. The
slop oil was separated into solid, water, and oil-soluble (indigenous oil)
products. The original slop oil was "unsuitable" for use in landfills, and the
C.9
-------
Carver-Greenfield Process
final solids product "met prevailing requirements" for use in nonhazardous
landfills (US EPA 1992a).
Approximately 18 kg (40 Ib) of slop oil sample (containing 12% solids)
was slurried with 36 kg (80 Ib) of solvent containing ~0.2 kg (0.4 Ib) of a
surfactant (US EPA 1992a). The slurry was subjected to evaporation to
reduce water content to less than 1%, then cooled and centrifuged.
The centrifuge cake was split into two samples. Solvent was extracted
once from sample 1 and twice from sample 2. Following extraction, the
samples were deoiled in a vacuum oven at 149°C (300°F). See table C.5 for
a summary of the product's composition following deoiling. The liquid
portion (solvent/indigenous oil mixture) was treated by evaporation and
steam stripping, resulting in an indigenous oil product with less than 0.8%
solvent (US EPA 1992a).
Two points should be noted regarding this study. First, the ratio of the
carrier solvent to solids was significantly high. Specifically, 36 kg (80 Ib)
of solvent was used, although the initial slop oil sample contained only «2.3
kg (5 Ib) of solids. This is higher than the 2.3 to 4.5 kg (5 to 10 Ib) of sol-
vent per 0.45 kg (1 Ib) ratio of the waste solids guideline for the SITE dem-
onstration (US EPA 1992a). Second, no information is presented
permitting quantification of amounts removed through evaporation and
Table C.5
Carver - Greenfield: Refinery Slop Oil Sample
Composifion by Weight Percent
Component
Solids
Indigenous
Hydrocarbons
Water
Solvent
Slop
Oil
120
16.0
720
0.0
Fresh
Slurry
3.9
5.3
237
67.1
Centrifuge
Cake
48
4.6
<1
47
Decontaminated Solids
Treated Treated
Once Twice
97.8 99.6
2.0 0.2
<0.1 <0.1
<01 <01
Compiled from US EPA 1992a, 0-2 and D-3
C.10
-------
Appendix C
deoiling effects, as opposed to amounts removed through solvent extraction.
This causes difficulties in evaluating the chemical/solvent extraction step.
In evaluating the Carver-Greenfield Process, however, the total removal
effected by all of the process steps should be considered.
CASE STUDY #3: PETROLEUM SLUDGE
Dissolved air flotation sludge, American Petroleum Institute (API) sepa-
rator bottoms, tank bottoms, biosludge, and primary/secondary emulsions
from a refinery were mixed in different proportions to produce three feeds
for treatability studies in 1984 (see table C.6). The feed was subjected to
two simulated stages of evaporation.
During the water evaporation, approximately 12% by weight of the in-
digenous oil was vaporized and condensed with the water.
The dry slurry was centrifuged. The centrifuged solids were then
reslurried in a carrier solvent (boiling point 188° to 193°C (370° to 380°F))
Table C.6
Carver - Greenfield: Petroleum Sludge
Parameter
Feed Materials
DAF Sludge
API Separator Bottoms
Tank Bottoms
Bio Sludge
Emulsions
Feed Components
Solids
Water
Indigenous oil
Total Feed Components
Deoiled Solids Product
Solids
Water
Indigenous oil
Solvent
Feed Mix A
(%)
26.5
00
00
10.2
63.3
(%)
15
44.0
57.6
103 1
(%)
95.5
<0.1
4.3
<01
Feed Mix B
(%)
26.5
0.0
12.3
10.2
510
(%)
1.6
35.2
638
100.6
(%)
96.0
<01
3.8
<0.1
Feed Mix C
(%)
26.5
2.9
00
11.3
56.4
(%)
21
44.7
53.2
100.0
(%)
94.4
<0.1
5.4
<0.1
Compiled from US EPA 1992a, D-5 and D-7. Feed Mix B 100.6% total feed components subtotal was
corrected from 99.6% cited in original source
C.11
-------
Carver-Greenfield Process
and filtered using a Buchner funnel. The filtered solids were deoiled in a
121 °C (250°F) vacuum oven. The final solids product contained 3.8 to
5.4% indigenous oil, reduced from initial indigenous oil-to-solid ratios in
the range of 25 to 40 (US EPA 1992a). Hazardous compounds present in
the feed such as benzene and phenol were reportedly removed from the
solids (US EPA 1992a).
According to Dehydro-Tech Corporation (DTC), the light indigenous oil
distilled during drying was used as the carrier oil/solvent (Trowbridge
1992).
It should be noted that this bench-scale test does not exactly simulate the
Carver-Greenfield Process as used in other studies (US EPA 1992a), since
the initial stages essentially involved subjecting the waste to evaporation
before slurrying with the carrier solvent. Again, no information was pre-
sented regarding amounts removed through evaporation (in the first stages)
or deoiling (in a heated, vacuum oven), as opposed to amounts removed
through the effects of extraction.
CASE STUDY #4: AMTRAK PETROLEUM HYDROCARBON AND
PCB CONTAMINATION
A former diesel fuel storage area was found to be contaminated with
petroleum hydrocarbons — soil and separate-phase contamination. As
reported by the developer, PCBs were found in concentrations of 5 to 360
ppm in the separate-phase hydrocarbons (Trowbridge, Holcombe, and
Kollitides 1991). Three samples containing 20 to 28% oil, 67 to 74% sol-
ids, and 4 to 6% water were treated through triple extraction/dehydration in
laboratory-scale testing. Resulting solids, in all cases, contained <1% oil,
and water was undetectable (Trowbridge, Holcombe, and Kollitides 1991).
In one sample, a PCB (Aroclor 1260) concentration was reduced from 7
ppm to less than 0.11 ppb in treated solids (Trowbridge, Holcombe, and
Kollitides 1991).
CASE STUDY #5: DRYING APPLICATIONS
Several case studies of the Carver-Greenfield System's use in commer-
cial operations are summarized here.
Wool Scouring Wastes. Wool scouring wastes and industrial activated
sludge were treated in a pilot-scale plant to assess treatment capabilities, as
C.12
-------
Appendix C
well as to evaluate recovery of lanolin from the oil in the wool scouring
waste. An 18:1 ratio of wool scouring waste-to-activated sludge was
treated (see table C.7). According to the developer, solvent is not detected
in the effluent water condensate (US EPA 1992a).
Table C.7
Carver - Greenfield: Commercial Plant
Parameter
Feed Composition Design
Water
Solids
Oil
Feed Flow Rate Design
Total Flow
Activated Sludge
(wt%)
85.0
12.8
2.2
(kg/h) (Ib/h)
983 2,213
Wool Scouring Waste
(Wt?c)
94.4
3.4'
221
(kg/h) (Ib/h)
17,699 39,822
Typical Operation Solids Product (%)
Water 0 6
Solvent 0.9
1 Expected feed composition was changed to 1 5% solids and <1% oil (versus design values of 3 4 and
2.2, respectively), and equipment was modified to accommodate this change
US EPA 1992a, Appendix D
The plant is designed with five evaporation stages. In the first three
stages, water is evaporated from the wool scouring waste without any sol-
vent present. Solvent is added in the fourth and fifth stages, and the acti-
vated sludge is added in the fifth stage. The stages were designed to
operate at 49°, 60°, 71°, 82°, and 127°C (120°, 140°, 160°, 180°, and 260°F).
Following centrifuging, solids are deoiled in three stages, and lanolin is
recovered in a solvent stripping unit.
Sewage Sludge Drying. Another application is the drying of sewage
sludge. As described by the developer, sewage sludge has a typical energy
content of 15,100 kJ/kg (6,500 Btu/lb) of dry solids, but moisture content
affects the accessibility of the energy. The Carver-Greenfield Process has
been used to dry sewage sludges, thereby producing a fuel with a net avail-
C.13
-------
Carver-Greenfield Process
able heat of almost 9,300 kJ/kg (4,000 Btu/lb) of solids. The dried sludge is
also combustible at high flame temperatures (1,100° to 1,650°C (2,000° to
3,000°F)), which destroy contaminants. Plants have been installed in sev-
eral cities, including Tokyo and Los Angeles (Holcombe and Kollitides
1991).
In Los Angeles, for example, the Carver-Greenfield Process was a part of
the Los Angeles Hyperion Energy Recovery System (HERS) project (Bress,
Greenfield, and Haug). The HERS, which converts sludge to gaseous and
solid sludge derived fuels (Bress, Greenfield, and Haug), was completed in
1987 (Harrison and Crosse 1991). The project was implemented to elimi-
nate disposal of the sludge at ocean outfalls.
After three years of operation, the HERS system enabled the city to
move from ocean disposal to 100% landfill and then to 100% beneficial
reuse of the sludge (Harrison and Crosse 1991). The reuse and disposal
options are intended to be applied flexibly and vary month to month
(Harrison, Smith, and Crosse 1990). For example, sludge reuse and dis-
posal allocations in July, 1989 were 30.6% land application, 31.7% energy
recovery, 19.9% landfilling, and 17.8% landfill cover. Those in August,
1989 were 46.8% land application, 22.2% energy recovery, with 14.5%
used in landfills, and 16.5% landfill cover (Harrison, Smith, and Crosse
1990). By January of 1991, energy recovery had increased to 56% of total
sludge, while 28% was applied to land, 9% was chemically fixed, and 7%
was used as compost (Harrison and Crosse 1991).
The HERS system produces gaseous fuel (methane) from anaerobic di-
gestion. As the system is designed, the digested sludge (containing 5%
solids) would be centrifuged to produce a cake consisting of 18 to 20%
solids, which would be ground and fluidized with a light solvent oil for
treatment by the Carver-Greenfield Process (Bress, Greenfield, and Haug).
According to the developer, three Carver-Greenfield Process trains; were
designed to treat 360 dry tonne/day (400 dry ton/day) of sewage sludge
from a population of 3.5 million (Holcombe and Kollitides 1991;
Trowbridge 1992). Another source, however, indicated that the design
capacity of the Carver-Greenfield facility was 241 dry tonne/day (265 dry
ton/day) and that this capacity had not yet been achieved. (According to
DTC, the design basis was 120 dry tonne/day (135 dry ton/day) per treat-
ment train with one on standby (Trowbridge 1992)). As a result, indirect
rotary steam dryers were recommended in order to augment the Carver-
C.14
-------
Appendix C
Greenfield drying capacity (Harrison, Smith, and Crosse 1990). The ongo-
ing work on the Carver-Greenfield Process is reportedly aimed at achieving
a final system capacity of 136 to 182 dry tonne/day (150 to 200 dry ton/day)
(Harrison, Smith, and Crosse 1990).
Four multieffect evaporation stages were designed to operate under var-
ied temperatures and pressures (under vacuum). Approximately 790 kJ are
expended per kilogram of water evaporated (340 Btu/lb), compared to 3,020
kJ/kg (1,300 Btu/lb) for indirect steam heated sludge dryers and 4,690 kJ/kg
(2,020 Btu/lb) for direct-fired sludge dryers. The resulting solids, which
have a heating value of around 13,000 kJ/kg (5,600 Btu/lb), are then sent to
a fluidized bed gasification system to generate power. Because pathogens
are destroyed, the potential for illnesses is reduced in comparison with that
of other processes that convert sludge to compost that have been reported
(Bress, Greenfield, and Haug).
The capital and operating costs reported for the entire HERS system
(including the Carver-Greenfield Process) in 1984 were «$187/dry tonne
($170/dry ton) of sludge fed. Of this, $24/dry tonne ($22/dry ton) were
operating costs, which were low because of the revenue from the generated
electricity (Bress, Greenfield, and Haug).
Peat Drying. Another application is drying peat, which contains bitu-
men, a commercial by-product. Peat is usually sun-dried, a method depen-
dent upon good weather. Laboratory- and pilot-scale studies disclosed that
iso-octanol was found to provide the best balance between bitumen extrac-
tion, fluidization, and costs (Holcombe and Kollitides 1991).
Alum Sludge Drying. The Carver-Greenfield Process is being used to dry
alum sludge under an agreement between Foster Wheeler USA and the
Contra Costa Water District (CCWD). The water district needed a method
of disposing of alum sludge, while Foster Wheeler was planning to con-
struct a cogeneration plant to generate electricity and steam for an oil refin-
ery (Lau 1991).
A two-stage system was installed. Low-pressure steam is used to dehy-
drate the alum sludge. The pressure reduction allows vaporization to occur
at lower-than-normal temperatures. Temperatures increase from 60°C
(140°F) in the first stage to 124°C (255°F) in the last, while the vacuum is
decreased. Because of the energy efficiency of the Carver-Greenfield Pro-
cess, total energy use can be less than 700 kJ/kg (300 Btu/lb) of water
C.15
-------
Carver-Greenfield Process
evaporated, compared to 4,650 kJ/kg (2,000 Btu/lb) for conventional sys-
tems (Lau 1991).
Following evaporation, a centrifuge removes half of the oil from the oil-
solids slurry. The sludge cake is then sent to a deoiler, which reduces car-
rier oil to 0.2 to 0.5% on the solids. During the first year of operations, the
extracted water had to be treated by the plant sewage system because of
carrier oil contamination. Modifications were then made in an attempt to
allow the water to be used in the plant cooling system instead (Lau 1991).
Unlike the sludge treated by the Carver-Greenfield unit that was installed
at the Los Angeles Hyperion plant, the CCWD sludge does not contain
sufficient organic material for burning as fuel. The alum sludge powder
was classified as nonhazardous. According to one source, some heavy met-
als appear to pass through the system, while others (cadmium, beryllium,
silver, selenium, and antimony) are either volatilized with the recovered
water or filtered by the carbon adsorption vent (Lau 1991). Mass balance
studies, however, would be required to characterize the removal process.
During the first 100 days after start up, the plant was operational for only
5 days. Problems included internal gumming, process line plugging, centri-
fuge seal leaks, centrifuge feed tube failure, and dust emissions from the
vent collector. Most of the problems were remedied. Apparently, gumming
occurred when the sludge slurry feed fell below 1 % solids. As a result, the
solids slurry was concentrated to 1.5 to 2% solids. About 570 L (150 gal)
of surfactant was added to prevent gumming. The optimal feed solids con-
centration is 3 to 4%; however, sludge pumping is difficult at concentra-
tions exceeding 3%. To avoid recurrence of start-up problems, the plant is
left in continuous operation, sometimes with minimum feed rates of 57 L/
min (15 gal/min). When the process is shut down, transfer pipes become
clogged and must be physically cleared (Lau 1991).
When the process is operating, 2% alum sludge is dehydrated to 98%+
solids. The thermal breakdown of aluminum hydroxide into aluminum
oxides further reduces the weight by 25%. The dried sludge was originally
disposed in landfills, costing $220/dry tonne ($200/dry ton) for hauling and
filling because the powder required sealed or pneumatic trucks. In addition,
the powder had to be treated with water and dust control additives in order
to be disposed of in landfills. An agreement was later reached enabling
reuse of the sludge powder in concrete and aggregate production, and dis-
posal costs dropped to $83/dry tonne ($75/dry ton) (Lau 1991).
C.16
-------
Appendix D
D
LOW-ENERGY EXTRACTION
PROCESS (LEEP®)
The following case studies present results of bench-scale treatability tests
of the LEEP treating a variety of contaminated materials. The data in this
summary were provided by the developer (Steiner and Rugg 1992). As
observed in Subsection 3.1.2.2, a pilot-scale study is underway; however,
no results were available for release at the time of this writing.
The treatability study results were based on leaching tests of soils con-
ducted to gauge the potential effectiveness of full-scale treatment.
CASE STUDY #1: MANUFACTURED GAS PLANTS (TAR CON-
TAMINATED SOIL)
During research and development of LEEP, the effectiveness of a variety
of solvent and solvent mixtures was tested. The developer currently uses
only acetone and a proprietary solvent in the LEEP system. However, the
results of one of the case studies which tested other solvent mixtures is
presented here to highlight some of the potential issues involved in applying
solvent extraction in general.
In the research study, solvent treatment of tar and PAH-contaminated
soils was tested. The tested solvents included acetone, acetone/methylene
chloride mixture, n-butylamine, acetone/n-butylamine mixture, acetone/
diethylamine mixture, solvent "X," solvent "Y," and solvent "Z" (Steiner
and Rugg 1992).
A baseline contamination profile was established by averaging the results
of gas chromatography/mass spectrometry (GC/MS) analyses (Method
8270) of three sample aliquots. Each aliquot consisted of leachate com-
bined from two soil samples. Based on contaminant solubility in the eight
different solvents, six multistage leaching schemes were designed. Each
D.I
-------
Low-Energy Extraction Process
experiment consisted of 10 stages. Table D.I outlines the leaching
schemes.
The results are summarized in table D.2 (on page D.3). The highest
removal efficiencies were achieved by Scheme 4 (acetone and an unidenti-
fied cosolvent mixture) and Scheme 6 (acetone and diethylamine mixture).
According to the developer, the elevated tentatively identified compound
(TIC) levels resulting from Scheme 5 (acetone and n-butylamine mixture)
appeared to be due to some kind of reaction between n-butylamine and the
soil (Rugg 1992). Although the targeted compounds were significantly
reduced in all cases (>90%), the research indicated that elevated TICs may
be an unwanted side effect. In addition, concentrations of some compounds
(such as naphthalene, di-n-butylphthalate, and di-n-octylphthalate) were
higher in a few end products than they were initially. As with other soil
treatment technologies, some of these differences may be attributed to the
natural variations in nonhomogenous soil. The research data indicates that
site-specific matrix effects should be tested. As noted earlier, the developer
of LEEP currently utilizes only acetone and a proprietary solvent (not one
of those tested in this case study) in the LEEP process.
CASE STUDY #2: CLAY SUBSOIL (POLYCHLORINATED EUPHENYL
(PCB)- CONTAMINATED SOLIDS).
A soil sample containing a PCB (Aroclor 1260) concentration of 1500
ppm was treated. The soil sample was composed of (by weight) 18% clay
Table D.I
LEEP Leaching Schemes
Stage
1
2
3
4
5-10
Scheme 1
A
Acetone
Acetone
Acetone
Acetone
Acetone
Scheme 2
A-Y-A
Acetone
Acetone
Y
Y
Acetone
Scheme 3
A-X-A
Acetone
Acetone
X
X
Acetone
Scheme 4
A-Z-A
Acetone
Acetone
Z
Z
Acetone
Scheme 5
A/B
Ac/N-butyl
Ac/N-butyl
Ac/N-butyl
Ac/N-butyl
Ac/N-butyl
Sc heme 6
A/D
Ac/diethyl
Ac/diethyl
Ac/diethyl
Ac/diethyl
Ac/diethyl
Reprinted by permission of Werner Steiner and Barry Rugg from "LEEP-Low Energy Extraction Process (Dr On-Site
Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the 85th Annual Meeting
and Exhibition, Kansas City, Missouri, June 21-26,1992. Copyright 1992 by Werner Steiner and Barry Rugg.
LEEP is a registered trademark of ART International, Inc
D.2
-------
Appendix D
Table D.2
LEEP Residual Soil Analyses After 10th Stage of
Leaching With Various Solvents
Concentration (ng/g)
Semivolatile
Compounds
Naphthalene
Acenaphlhylene
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Di-N-butylphthalate
Fluoranthene
Pyrene
Benzo(a)anthracene
Bis(2-ethylhexyl)phthalate
Chrysene
Di-N-octylphthalate
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Ideno( 1 ,2,3-cd)pyrene
Di-benzo(a,h)anthracene
Benzo(g,h,i)perylene
Subtotal BNs1
TICs2 (Other than BNs)
Total
BN Removal (%)
TIC Removal (%)
Total Removal (%)
Baseline
10.20
8.27
173
602
19.20
7.17
2.46
11.03
22.06
976
908
1225
0.73
11.50
4.46
9.96
2.73
043
246
151 50
230.61
382.11
-
Scheme 1
A
075
0.29
0.07
037
014
4.00
012
0.20
007
016
0.09
005
0.05
5.91
34.89
40.80
96.1%
849%
89.3%
Scheme 2
A-Y-A
0.30
006
0.14
2.00
005
008
1.05
2.61
43.32
45.93
983%
812%
880%
Scheme 3
A-X-A
0.27
0.13
3.51
0.07
2.69
1.18
6.84
6.84
95.5%
982%
Scheme 4
A-Z-A
0.20
0.13
015
0.07
1 75
0.08
0.09
1.06
0.08
2.20
0.21
2.41
98.5%
99.9%
99.4%
Scheme 5
A/B
10.78
0.37
1.33
1.05
0.14
12.77
2261.58
2274.35
91.6%
neg.
neg.
Scheme 6
A/D
0.07
0.29
0.14
0.23
0.23
99.8%
-
99.9%
1 BNs are the family of targeted chemical compounds classified as base neutral soluble semivolatiles
and listed above.
2 TICs are Tentatively Identified Compounds which were not specifically targeted (reported as sum of all
TICs In the sample).
neg. - negative removal efficiency (treated concentration greater than initial concentration)
NOTE Leaching solvents for each scheme were as follows acetone (scheme 1), acetone and
unidentified co-solvent mixtures (schemes 2, 3, & 4), acetone and n-butylamine (scheme 5),
and acetone and diethylamme (scheme 6)
Reprinted by permission of Werner Sterner and Barry Rugg from "LEEP-Low Energy Extraction Process for
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the
85th Annual Meeting and Exhibition, Kansas City, Missouri, June 21-26,1992 Copyright 1992 by Werner
Steiner and Barry Rugg.
LEEP is a registered trademark of ART International, Inc.
D.3
-------
Low-Energy Extraction Process
(particles, <5 |4m), 52% silt (particles from 5 urn to 50 jam), and 30% sand
(particles from 50 urn to 500 |Jm). See table D.3 for the resulting leaching
removal efficiencies.
CASE STUDY #3: INDUSTRIAL LANDFILL (PCB-CONTAMINATED
SOLIDS)
A sample of landfill material contaminated with PCBs (Aroclor 1254 and
1260), semivolatile organics, and heavy metals was treated. The sample
was composed of (by weight) 40% water and soil [17% clay (<5 urn), 55%
silt (5 to 50 nm), and 28% larger particles (>50 jam)]. The initial concentra-
tions of contaminants on a dry weight basis were as follows: 10,584 ppm
PCBs and 1,078 ppm semivolatiles [the semivolatiles concentrations were
469 ppm TICs and 609 ppm specifically identified base neutral (BN)
soluble semivolatiles].
The developer calculated the total amount of contaminants removed as
the sum of the amounts of contaminants removed from each stage. Specifi-
cally, the "concentration remaining in the soil" after each stage was calcu-
lable D.3
LEEP Multistage PCS Leaching Results From Clay
Stage
#
1
2
3
4
5
6
7,8,9
PCB Removed
Per Stage
dg)
19,155
3,678
1,318
245
157
69
10
Total PCB
Removed
(Ig)
19,155
22.833
24,150
24,395
24,552
24,621
24,631
Stage
Leaching
Efficiency1
(%)
78
67
73
51
67
88
99+
Overall
Leaching
Efficiency2
(%)
78
93
98
99
997
999
99.9+
1 The Stage Leaching Efficiency is the amount of contaminant removed in each stage divided by the
initial amount of contaminant in that stage
2. The Overall Leaching Efficiency is the total (cumulative) amount leached divided by the initial amount of
contaminant in the sample.
Reprinted by permission of Werner Stemer and Barry Rugg from "LEEP-Low Energy Extraction Process for
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Stemer and Barry Rugg, presented at the
85th Annual Meeting and Exhibition, Kansas City, Missouri, June 21-26,1992 Copyright 1992 by Werner
Steiner and Barry Rugg.
LEEP is a registered trademark of ART International, Inc.
D.4
-------
Appendix D
lated based on the dry sample weight, assuming that all of the contaminants
(including contaminants in the residual leaching solvent) were those in the
soil. Actual soil concentrations, based on separate analyses, were presented
only for the 12th stage, where the concentrations were determined by ana-
lyzing the air-dried residual soil (Steiner and Rugg 1992). No information
regarding mass balance closure was presented, and therefore, an indepen-
dent review of the data was not possible (for example, to quantify potential
contaminant remnants in the residual solvent or to serve as a cross-check on
the calculated staged removal efficiencies).
Table D.4 presents the efficiencies effected in removing BN, and table
D.5 (on page D.6), those in removing PCBs. After three stages of treat-
Table D.4
LEEP Base Neutral (Semivolatile) Leaching: Industrial Landfill
BN
Removed
Stage Per Stage
# (Mg)
1 2,218
2 1,178
3 520
4 232
5 112
6 52
7 to 12 224
Total BN
Removed
(tig)
2,218
3,396
3,916
4,148
4,260
4,312
4,536
BN cone.
Remaining
in Soil
(ppm)1
387
269
217
194
183
177
15"
Initial BN concentration in the sample (excluding TICs)
Wet sample weight
Dry sample weight
Leaching solvent volume
Stage leaching time
Stage
Leaching
Efficiency
(%)2
36
30
19
11
6
3
12
609 ppm
16.7 g
I0g
40 mL
Ihr
Overal
Leaching
Efficiency
(%)3
36
56
64
68
70
71
98
1 The BN Concentrations shown in this column are calculated based on the dry sample weight, assuming
all BNs, including those in the residual leaching solvent, to be associated with the solids
2. The Stage Leaching Efficiency is the amount of contaminant removed in each stage divided by the initial
amount of contaminant in that stage.
3 The Overall Leaching Efficiency is the total (cumulative) amount leached divided by the initial amount of
contaminant in the sample.
4. The BN concentration in the sample after the 12th stage was determined by analyzing the air dried
residual soil.
Reprinted by permission of Werner Steiner and Barry Rugg from "LEEP-Low Energy Extraction Process for
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the 85th
Annual Meeting and Exhibition, Kansas City, Missouri. June 21-26,1992. Copyright 1992 by Werner Steiner
and Barry Rugg.
LEEP is a registered trademark of ART International, Inc.
D.5
-------
Low-Energy Extraction Process
Table D.5
LEEP PCBs Leaching: Industrial Landfill
Stage
#
1
2
3
4
5
6
7 to 12
PCBs
Removed
Per Stage
dg)
71,500
30,300
10,850
3,640
635
232
277
Total PCBs
Removed
dg)
71,500
101,800
112,650
116,290
116,925
117,157
117,434
PCBs cone.
Remaining
in Soil
(ppm)1
4593
1568
483
119
56
33
4.8"
Stage
Leaching
Efficiency
(%)2
60.86
65.89
69.19
75.33
53.27
41.56
85.23
Overal
Leaching
Efficiency
(%)3
60.86
86.60
95.89
98.98
9952
9972
9996
Initial BN concentration in the sample (excluding TICs) 10,584 ppm
Wet sample weight 16 7 g
Dry sample weight 10 g
Leaching solvent volume 40 niL
Stage leaching time 1 hr
1 The PCBs Concentrations shown in this column are calculated based on the dry sample weight,
assuming all PCBs, including those in the residual leaching solvent, to be associated with the solids
2 The Stage Leaching Efficiency is the amount of contaminant removed m each stage divided by the
initial amount of contaminant in that stage
3 The Overall Leaching Efficiency is the total (cumulative) amount leached divided by the initial amount of
contaminant in the sample.
4 The PCBs Concentration in the sample after the 12th stage was determined by analyzing the air dried
residual soil.
Reprinted by permission of Werner Sterner and Barry Rugg from "LEEP-Low Energy Extraction Process tor
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the
85th Annual Meeting and Exhibition, Kansas City, Missouri. June 21-26, 1992. Copyright 1992 by Werner
Steiner and Barry Rugg
LEEP is a registered trademark of ART International, Inc
ment, the overall removal of BN was only 64% (up from 36% in the first
stage), while the overall removal of PCBs increased from 61% in the first
stage to 96% in the third stage. After the 12th stage, when the soil was
analyzed, removal of 98% BN was achieved, and 99.96% of PCBs (Steiner
and Rugg 1992; Mallach 1992).
D.6
-------
Appendix D
CASE STUDY #4: REFINERY SLUDGES (OIL & GREASE,
SEMIVOLATILE ORGANIC CONTAMINATION, VOLATILE OR-
GANIC CONTAMINATION, AND METALS — AS, CD, CU, PB, ZN,
Nl, V, AND CR)
Two refinery sludge samples were treated. Sludge #1 consisted of the
solids fraction from a rainwater impoundment. Its initial composition was
33% solids, 60% water, and 7% oil and grease. Sludge #2 consisted of an
emulsion filter cake from slop recovery waste having an initial composition
of 47% solids, 28% water, and 25% oil & grease. The sludges were con-
taminated with various semivolatile compounds, including anthracene,
benzo-a-anthracene, benzo-a-pyrene, bis-2-ethylhexyl-phthalate, chrysene,
naphthalene, phenanthrene, and pyrene, along with volatile organics and
metals (Steiner and Rugg 1992).
Table D.6 presents the efficiencies effected in removing semivolatiles,
and table D.7 (on page D.8), those in removing oil and grease. No data
regarding removal of the volatile compounds and metals were presented.
Table D.6
LEEP Semivolatile Organic Compounds Leaching: Refinery Sludges
Sludge*] Sludge #2
Stage #
1
2
3
4
5
6
7
8
Stage Efficiency1
71.1
753
597
40.5
29.9
Overall Efficiency2
71 1
927
972
98.4
98.9
999+
Stage Efficiency1
61.9
43.1
74.4
51.7
32.9
574
45.7
Overall Efficiency2
61.9
78.0
94.4
97.8
98.1
992
99.5
99.9+
1 The Stage Efficiency is the amount of contaminant removed in each stage divided by the
initial amount of contaminant in that stage
2. The Overall Efficiency is the total (cumulative) amount leached divided by the initial amount of
contaminant in the sample
Reprinted by permission of Werner Steiner and Barry Rugg from "LEEP-Low Energy Extraction Process for
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the
85th Annual Meeting and Exhibition, Kansas City, Missouri, June 21-26,1992 Copyright 1992 by Werner
Steiner and Barry Rugg
LEEP is a registered trademark of ART International, Inc
D.7
-------
Low-Energy Extraction Process
Table D.7
LEEP Oil And Grease Leaching: Refinery Sludges
Sludge #1 Sludge #2
Stage* Stage Efficiency1 Overall Efficiency2 Stage Efficiency1 Overall Efficiency2
1
2
3
4
5
6
7
26.6
57.1
62.9
65.8
667
26.6
684
88.4
96.0
98.4
999+
239
42.9
50.7
48.8
515
64 1
999+
23.9
58.4
78.5
88.9
94.7
98.2
1. The Stage Efficiency is the amount of contaminant removed in each stage divided by the
initial amount of contaminant in that stage
2. The Overall Efficiency is the total (cumulative) amount leached divided by the initial amount of
contaminant in the sample.
Reprinted by permission of Werner Steiner and Barry Rugg from "LEEP-Low Energy Extraction Process for
On-Site Remediation of Soil, Sediment, and Sludges" by Werner Steiner and Barry Rugg, presented at the
85th Annual Meeting and Exhibition, Kansas City, Missouri, June 21-26,1992. Copyright 1992 by Wernei
Steiner and Barry Rugg
LEEP is a registered trademark of ART International, Inc
The developer noted, however, that materials were decontaminated below
regulatory limits (Steiner and Rugg 1992).
The most significant gains in the efficiency in semivolatile removal were
again observed in the first three stages of treatment. Efficiencies increased
from the 62 to 71% range in the first stage to the 94 to 97% range after
three stages. Efficiencies exceeding 99.9% were achieved in treating
Sludge #1 after 6 stages, while 8 stages were required to attain this level in
treating Sludge #2.
Efficiencies in removing the oil and grease increased more gradually
initially than those in removing semivolatiles. For example, efficiencies in
removing oil and grease of only 24 to 27% were attained after one stage,
while those in removing semivolatiles were 62 to 71%. But 99.9% effi-
ciency was attained in removing the oil and grease from Sludge #1 after 6
stages, and from Sludge #2, after 7 stages.
D.8
-------
Appendix D
CASE STUDY #5: WAUKEGAN HARBOR SEDIMENT (PCB CON-
TAMINATION)
During the early development of the LEEP system a treatability study on
sediment from Waukegan Harbor demonstrated 99.9% removal of a PCB.
The PCB-contaminated (Aroclor 1242) sample had an initial concentration
of 33,641 ppm PCBs (dry weight basis) and consisted of 42% water by
weight (Steiner and Rugg 1992).
D.9
-------
-------
Appendix E
E
NUKEM DEVELOPMENT (NKD)
PROCESSES
This appendix presents the results of NKD Process pilot plant treatability
studies carried out on (1) seven soils, all contaminated with polychlorinated
biphenyls (PCBs), (2) two refinery feedstocks, (3) an American Petroleum
Institute (API) separator sludge, and (4) a slop oil sludge.
The following soils were tested:
• Four soils taken at varying depths from the General Electric
Rose Superfund Site in Pittsfield, Massachusetts (RS-10, RS-14,
RS-16, RS-18);
• One soil from a Superfund site in Texas;
• One soil from a Superfund site in New Jersey; and
• One soil from a site in Mississippi.
These samples were selected to enable study of a wide range of key
properties that could be expected to affect the performance of the process.
Table E. 1 (on page E.2) presents the properties of the seven soils before
treatment. Table E.2 (on page E.2) indicates the particle size distributions
of three of the soils taken from the Rose Superfund Site.
Extraction tests were performed in bench-scale equipment utilizing 30-
gram samples of contaminated soil. The contaminated soil, as received,
was placed in a container and mixed with a small amount of reagent and a
measured amount of fresh solvent. Solvent-to-soil loadings varied from 1:1
to 2:1 by weight. The mixture was agitated for approximately three minutes
and allowed to settle. The solvent was then separated from the soil by de-
cantation, and a sample of the soil was drawn for PCB analysis. This proce-
E.l
-------
NuKEM Development (NKD) Processes
Table E.I
NKD Process Properties of Test Soils
Test Soil
Massachusetts
SojJ
•RS-10
•RS-14
•RS-16
•RS-18
Mississippi Soil
New Jersey Soil
Texas Soil
Appearance
Sandy
Clayey
Sandy
Clayey
Clayey
Silty
Clayey, high
plasticity
Physical Properties (As Received)
Moisture
(Wt %)
84
135
11.5
26.5
15.0
150
250
Oil & Grease
(Wt %)
NA
03
04
3.6
NA
NA
Trace
Dry Specific
Gravity
NA
1.61
2.50
1 32
NA
NA
NA
Initial PCBs
(m.g/kg)
3,300
771
1,147
3,130
41
1 944
50
Table E.2
NKD Process Particle Size Distribution of Selected Test Soils
Particle Size (mm)
Rose Site Test Soils (Wt %)
>2
200-0861
0841-0.420
0 420-0 250
0.250-0 177
0.177-0 149
0.149-0 125
0105-0.074
<0074
RS-14
188
74
49
39
2.8
1.8
1 8
59
497
RS-16
49.25
1350
7 10
4.10
2.20
1.10
1.00
2.20
18.10
RS-18
17.9
19.9
126
7.6
3.6
1.8
22
3.5
28.9
dure, constituting a single stage of extraction, was repeated as many times
as necessary to achieve a desired overall level of decontamination.
Stage-by-stage batch extraction results are set forth in table E.3 (on page
E.3). Although not all tests were continued to completion, each of the test
E.2
-------
Appendix E
soils was determined to be treatable to residual PCBs levels of less than 2
mg/kg. With the exception of PCBs and oil and grease concentrations, the
properties of each soil were essentially unaffected by the treatment process.
In particular, moisture and clay plasticity were essentially unchanged.
The concentrations of PCBs in the Rose Superfund Site samples ranged
from 771 to 3,131 mg/kg. After four stages of extraction, the residual PCBs
concentrations in these samples were all less than 25 mg/kg. As the results
for Sample RS-10 illustrate, when processing was carried to completion,
residual PCBs levels were reduced to less than 2 mg/kg. Essentially all oil
and grease were removed from each of the Rose Superfund Site samples.
Table E.3
Batch Extraction Performance of NKD Soil Washing Process
(PCB Concentration in mg/kg)
Extraction
Stage
0
1
2
3
4
Massachusetts Soils
RS-10
3.300
330
40
4
0
RS-14
771
245
67
23
8
RS-16
1,147
368
163
56
22
Mississippi
Soil
RS-18
3,131 41
298 11
58 45
25 1.6
7
New Jersey
Soil
1,944
291
48
8
1
Texas
Soil
50
10
0
-
-
After two stages of extraction, no residual PCBs could be detected in the
sample of the Texas soil, although this soil was particularly difficult to treat
(clay material with a high moisture content and a high plasticity).
The pilot countercurrent extraction column, described in Subsection
3.13.3, was used to treat two refinery waste streams, an API separator
sludge, and a slop oil sludge. The pilot plant also contained a complete
fractional distillation column for the processing, recovery, and recycle of
solvent, along with a number of dewatering devices, including a plate and
frame filter press, a belt filter press, and a vacuum filter.
E.3
-------
NuKEM Development (NKD) Processes
The basic characteristics of the two refinery feedstocks are listed in table
E.4.
The API separator sludge was taken directly from the API separator pit
of a major Gulf Coast refinery. The sample of slop sludge was taken from a
waste oil dumping pit at another major Gulf Coast refinery.
Table E.4
Characteristics of Two Refinery Feedstocks
Component
% Water
% Solids
%Oil
API Separator
(Primary)
81%
9%
10%
Slop Sludge
(Secondary)
78%
16%
6%
Characteristics of the product oils recovered from the samples of API
separator and slop oil sludge, as determined from the form of true boiling
point curves, varied significantly. The oil recovered from the sample of
slop sludge was heavier than that recovered from that of API separator
sludge.
Residual hydrocarbon characteristics of the solids and the water pro-
duced in the treatment of API separator sludge are presented in table E.5.
Included for comparison purposes are applicable solid and water best dem-
onstrated available control technology (BDAT) standards. Only four com-
pounds are present at or above the levels of analytical detection, and only
one of these compounds, phenol, is regulated. The BDAT requirements
were met. Basic chromatographic data suggested that similar results could
be expected for the products of slop sludge processing. Table E.5 shows
that the NKD Process effects a high level of removal of oil from both water
and solids present in raw API separator sludge.
E.4
-------
Appendix E
Table E.5
Fate of Organics in Pilot-Scale Treatment of API Separator Sludge
Benzene
Ethyl Benzene
Toluene
Xylene
Phenol
bis-(2-Chloroethyl) Ether
4-Methylphenol (p-cresol)
2-Nitrophenol
2,4- Dimethylphenol
bis-(2-Chloroethoxy) Methane
2,4-Dichlorophenol
Naphthalene
4-Chloroanilme
2-Methyl naphthalene
4-Chloro-3-methylphenol
2,4,5-Trichlorophenol
2-Chloronaphthalene
2-Nitroaniline
3-Nitroaniline
2.4 Dinitrophenol
Dibenzofuran
2,4-Dinitrotoluene
4,-Nitrophenol
Fluorene
-Chlorophenyl-4
-Nitroaniline
4,6-Dintro-2-merhylphenol
N-Nitrosodiphenylamine
Phenanthrene
Anthrancene
Dibutyl Phthalate
Pyrene
Benzo(a)anthracene
Chrysene
3,3'-Dichlorobenzidine
bis-(2-ethylhexyl) Phthalate
di-n-octyl Phthlate
Benzo(a)pyrene
Indeno( 1 ,2,3-cd)pyrene
Benzo(g,h,i)perylene
Raw
Sludge
434
142
359
939
16.41'
1.16
1.08
5.03
5.55
1.5
10.40
1.00
7.78
79.5
1 7
2.39
1.78
20.8
22.2
8.02
1.11
20.3
43.3
ND
1.06
102.5
5.76
ND
167
ND
2.9
ND
2.91
1.37
531
ND
ND
1.88
3.10
Filtered
Solids
ND
ND
ND
ND
3.35'
ND
ND
ND
ND
ND
ND
ND
ND
272
ND
ND
ND
0.79
ND
ND
ND
ND
1.62
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Filtered
Water
ND
ND
ND
ND
0.581
ND
0.09
ND
ND
ND
ND
ND
ND
03
ND
ND
ND
0.09
0.08
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
010
ND
ND
ND
ND
ND
0.08
ND
ND
ND
BOAT Standard
Solid Water
14 0.011
14 0.011
14 0.011
22 0.011
3.6 0.047
-
-
-
42 0.033
-
-
-
-
-
-
-
0.054
-
-
34 0.039
28 0.039
3 6 0.06
14 0.011
20 0.043
1 50.043
-
7.3 0.043
-
12 0.047
-
-
1. The phenol readings reported are highly suspect Extremely low levels of phenol were reported in the raw sludge
(ppm) Phenol is highly soluble in water; it is also soluble in NKD process solvent. In spite of this and the very
large quantities of both present, the analytical data suggest limited dissolution of phenol
E.5
-------
NuKEM Development (NKD) Processes
Characteristics of metals of the solids produced in the treatment of API
separator sludge in the NKD Process pilot plant are presented in table E.6.
These were preliminary results, but showed that stabilization of solids at
and below BDAT standards is readily achievable.
Table E.6
Leachability of Metals in Samples of Pilot Scale
Processed API Separator Solids
TCLP, ppm
Ag
As
Ba
Cd
Cr
Hg
Ni
Pb
Se
Metal Content of
Dry Solids, ppm
< 1
52
940
5.7
220
35
75
100
1.0
Stabilized '»
Sample
<0.01
001
1.6
<0.01
<0.02
<0001
<0.02
<0025
< 0.005
Detection Limit
001
0.002
0.02
001
0.02
0.001
0.02
0.025
0.005
1 Test sample was stabilized with 0 5 units of stabilizing chemicals per unit of filter wet solids Results clearly
indicate that substantially less stabilizing chemical is needed to comply with the BDAT requirements. Optimization
work is underway now to determine minimum quantity of stabilizing chemicals required for BDAT level
stabilization
2 Stabilization resulted in a 15 percent increase in the volume of the solids.
>U.S. GOVERNMENT PRINTING OFFICE: 1995-620-997/82069
E.6
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