Environmental Remediation. Removing Organic and Metal Ion Pollutants 9780841224797, 9780841213654, 0-8412-2479-X

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Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

Environmental Remediation

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

ACS

SYMPOSIUM

SERIES

509

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

Environmental Remediation Removing Organic and Metal Ion Pollutants G. F. Vandegrift,

EDITOR Argonne National Laboratory

D. T. Reed, EDITOR Argonne National Laboratory

I. R. Tasker, EDITOR National Institute for Petroleum and Energy Research

Developed from a symposium sponsored by the Division of Industrial and Engineering Chemistry, Inc., at the 201st National Meeting of the American Chemical Society, Atlanta, Georgia, April 14-19, 1991

American Chemical Society, Washington, DC 1992

Library of Congress Cataloging-in-Publication Data Environmental remediation: removing organic and metal ion pollutants / G. F. Vandegrift, ed., D. T. Reed, ed., I. R. Tasker, ed. p.

cm.—(ACS Symposium Series, 0097-6156; 509).

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

"Developed from a symposium sponsored by the Division of Industrial and Engineering Chemistry, Inc., at the 201st National Meeting of the American Chemical Society, Atlanta, Georgia, April 14-19, 1991." Includes bibliographical references and indexes. ISBN 0-8412-2479-X 1. Water, Underground—Purification—Congresses. 2. Soil pollution—Congresses. 3. Separation (Technology)—Congresses. 4. Bioremediation—Congresses. I. Vandegrift, G. F. (George F.), 1945. II. Reed, Donald Timothy, 1956- . III. Tasker, I. R. (Ian R.), 1954- . IV. American Chemical Society. Division of Industrial and Engineering Chemistry. V. American Chemical Society. Meeting (201st: 1991: Atlanta, Ga.). VI. Series. TD426.E59 1992 628.5'.2—dc20

92-27219 CIP

The paper used in this publication meets the minimum requirements of American National Standard for Information Sciences—Permanence of Paper for Printed Library Materials, ANSI Z39.48-1984. Copyright © 1992 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per-copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, MA 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of thefirstpage of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA

1992 Advisory Board ACS Symposium Series M . Joan Comstock, Series Editor

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

V. Dean Adams Tennessee Technological University Mark Arnold University of Iowa David Baker University of Tennessee

Bonnie Lawlor Institute for Scientific Information John L. Massingill Dow Chemical Company Robert McGorrin Kraft General Foods

Alexis T. Bell University of California—Berkeley

Julius J. Menn Plant Sciences Institute, U.S. Department of Agriculture

Arindam Bose Pfizer Central Research

Vincent Pecoraro University of Michigan

Robert F. Brady, Jr. Naval Research Laboratory

Marshall Phillips Delmont Laboratories

Margaret A. Cavanaugh National Science Foundation

A. Truman Schwartz Macalaster College

Dennis W. Hess Lehigh University

John R. Shapley University of Illinois at Urbana-Champaign

Hiroshi Ito IBM Almaden Research Center Madeleine M. Joullie University of Pennsylvania Mary A. Kaiser Ε. I. du Pont de Nemours and Company Gretchen S. Kohl Dow-Corning Corporation

Stephen A. Szabo Conoco Inc. Robert A. Weiss University of Connecticut Peter Willett University of Sheffield (England)

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.fw001

Foreword 1HE A C S S Y M P O S I U M S E R I E S was first published in 1974 to provide a mechanism for publishing symposia quickly in book form. The purpose of this series is to publish comprehensive books developed from symposia, which are usually "snapshots in time" of the current research being done on a topic, plus some review material on the topic. For this reason, it is necessary that the papers be published as quickly as possible. Before a symposium-based book is put under contract, the proposed table of contents is reviewed for appropriateness to the topic and for comprehensiveness of the collection. Some papers are excluded at this point, and others are added to round out the scope of the volume. In addition, a draft of each paper is peer-reviewed prior to final acceptance or rejection. This anonymous review process is supervised by the organizer(s) of the symposium, who become the editor(s) of the book. The authors then revise their papers according the the recommendations of both the reviewers and the editors, prepare camera-ready copy, and submit the final papers to the editors, who check that all necessary revisions have been made. As a rule, only original research papers and original review papers are included in the volumes. Verbatim reproductions of previously published papers are not accepted. M. Joan Comstock Series Editor

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.pr001

Preface I H E U N I T E D S T A T E S H A S S U F F E R E D severe environmental damage as a result of industrial growth and defense-related activities. Cleanup costs are estimated to be as high as a trillion dollars. Our damage to the environment is already affecting our health and welfare, and it must be repaired to ensure our survival. The U.S. Environmental Protection Agency estimates that more than 75,000 registered hazardous waste generators and more than 25,000 possible hazardous waste sites exist in the United States. Although the situation is ominous, it has encouraging aspects. Environmental remediation and waste avoidance technologies are rapidly increasing growth areas. Potentially great benefits await those who can develop economical, effective, and efficient solutions to these problems. The symposium on which this volume is based acknowledged the growing importance of environmental remediation and reflected our belief that separation science will continue to play a key role in the remediation of contaminated aquifers, as well as surface and subsurface media. The wide variety of developing technologies discussed will provide the newly initiated with an understanding of the breadth of the problems and potential solutions and will widen the perspective of those already in the field. The various chapters cover the following topics: improvements and applications of existing separation technology, developing technologies, applications of separation science to waste minimization and preconcentration, basic research applied to understanding the chemistry behind new technologies, and analysis of the hazards present in the environment. Chapter 1 presents an overview of the extent of our abuse of the environment, the high cost of its cleanup, and the federal regulations that govern cleanup and disposal of present waste. It also summarizes some recently published common-sense suggestions on how we should proceed. The table of contents illustrates the breadth of this volume. About one-third of the chapters deal directly with remediation technologies for groundwater and soil decontamination; another third deal with waste treatment avoidance technologies; and the last third discuss fundamental research for developing new technologies or for measuring the problem or the effectiveness of the treatment. This book will provide a contribution to this important field and will reemphasize the need for continued progress and development.

xi

We acknowledge the efforts of two extremely capable, amiable, and uncountable ladies and thank them for their hard work, their persistence, and their goodwill throughout this endeavor. The first is Donna Tipton—who kept our correspondence organized, handled the typing load and much of the telephone communication, and made excuses for us to Anne Wilson—who has been helpful, tough but gracious, and persistent in moving this publication along. G . F. VANDEGRIFT

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.pr001

Chemical Technology Division Argonne National Laboratory Argonne, I L 60439 D. T. REED Chemical Technology Division Argonne National Laboratory Argonne, I L 60439 I. R. TASKER National Institute for Petroleum and Energy Research IIT Research Institute P.O. Box 2128 Bartlesville, O K 74005 June 19, 1992

xii

Chapter 1

Environmental Restoration and Separation Science 1

2

1

1

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

D. T. Reed , I. R. Tasker , J . C. Cunnane , and G. F. Vandegrift

1Chemical Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 National Institute for Petroleum and Energy Research, IIΤ Research Institute, P.O. Box 2128, Bartlesville, OK 74005 2

The problem of environmental restoration, s p e c i f i c a l l y the cleanup of contaminated s o i l s and groundwaters, i s one of the most important technical and s o c i e t a l problems we face today. To provide a background to t h i s problem, the extent and cost, laws and regulations, important contami­ nants, and key issues i n environmental restoration are discussed. A b r i e f introduction to the role of separation science, i n r e l a t i o n to environmental restoration, i s also given.

The cleanup of anthropogenic contaminants that are present i n the environment i s one of the most important problems that we face today. These contaminants can cause a wide range of p o l l u t i o n problems, including global climate change, ozone depletion, e c o l o g i c a l deterioration, and groundwater contamination. The remediation of existing waste, along with concerns over the fate of waste we are currently generating or plan to generate, i s recognized by the public as the leading environmental issue of today (1,2). The applications of separation science to environmental restoration are centered on the cleanup of contaminated groundwaters and s o i l s . The extent and complexity of the groundwater contamination problem continues to present formidable technological obstacles to cleanup. The most important factors that contribute to t h i s complexity are the large number of contaminated s i t e s , the wide d i v e r s i t y of the contaminants present i n those s i t e s , the inherent complexity of the subsurface chemistry of the contaminants, and the d i f f i c u l t y i n interpreting e x i s t i n g regulations to e s t a b l i s h compliance and properly p r i o r i t i z e s i t e remediation e f f o r t s . Separation science has already had an important role i n the cleanup of contaminated groundwater and s o i l . I t has been

0097-6156/92/0509-0001$06.00A) © 1992 American Chemical Society

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

2

ENVIRONMENTAL REMEDIATION

successfully applied to solve a wide variety of s p e c i f i c groundwater contamination problems. However, when one takes into consideration the l i m i t a t i o n s of these "successes", and considers the magnitude and complexity of the cleanup problem that we face today, i t i s evident that current technology i s inadequate. In t h i s context, the need for greater emphasis on the development of new and improved technology has never been greater. By i t s very nature, separation science and technology draws upon the knowledge derived from a large number of science and engineering d i s c i p l i n e s . A comprehensive review of t h i s f i e l d would be an enormous task, and we make no claim to such an objective i n preparing t h i s chapter. Rather, i t i s our objective to provide background information on subsurface contamination and introduce the role of separation science. To t h i s end, we discuss the magnitude and costs associated with the groundwater contamination problem, the regulatory requirements that drive remediation e f f o r t s , important organic and inorganic contaminants, issues associated with environment restoration and give a general l i s t i n g of separation techniques that may apply to environmental restoration. To the extent possible, the reader i s provided key references for more detailed discussions of the various aspects of t h i s important f i e l d . Extent and Cost of Environmental

Remediation

The l i s t of s i t e s that need to undergo environmental restoration i s long and rapidly growing. In 1991» the U.S. Environmental Protection Agency (EPA) (3-5) had estimated that i n the United States there are over 500,000 hazardous chemicals i n use today; over 75,000 registered hazardous waste generators; and over 4500 hazardous waste treatment, storage, and disposal f a c i l i t i e s . This i s further complicated by the number of e x i s t i n g hazardous waste s i t e s . Current estimates, which are acknowledged to be low, are that there are over 25,000 possible hazardous waste s i t e s (4). Another 52,000 municipal l a n d f i l l s , 75,000 on-site i n d u s t r i a l l a n d f i l l s , 180,000 s i t e s with underground storage tanks, and 60,000 abandoned mines s t i l l need to be evaluated more thoroughly. There i s also increased recognition of the extent of environmental contamination within the Department of Energy (DOE) complex (6-Θ). Radioactive groundwater plumes have been i d e n t i f i e d i n the subsurface at many DOE f a c i l i t i e s . Remediation e f f o r t s and the e f f o r t s to develop new and improved technologies have been greatly emphasized by DOE i n the l a s t few years (6). The o v e r a l l waste management problem within the DOE i s compounded by the existence of large amounts of radioactive, hazardous, and radioactive/hazardous mixed waste currently either awaiting f i n a l disposal or requiring processing p r i o r to f i n a l disposal. Recent estimates of these waste inventories have i d e n t i f i e d 180 waste streams and the need for the disposal of over 700,000 m-* of waste (Θ). The majority of t h i s waste (>99Z) i s located at Hanford i n Washington; Rocky F l a t s i n Colorado; Idaho National Engineering Laboratory i n Idaho; Y-12, K-15 and Oak Ridge National Laboratory i n Tennessee; and the Savannah River Plant i n North Carolina.

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1. REED ET AL.

Environmental Restoration and Separation Science 3

Associated with the large number of p o t e n t i a l waste cleanup s i t e s are the r i s i n g cost estimates f o r the environmental restoration of these s i t e s . The methodology by which the cost of cleanup and environmental restoration i s determined i s i t s e l f a controversial issue. Numerous estimates, based on a wide v a r i e t y of assumptions, can be found i n the l i t e r a t u r e . The trend i n cost estimates, however, i s quite readily discerned. In the early summer of 1991, the costs generally quoted f o r environmental restoration were i n the $70-250 b i l l i o n range. By November of the same year (9), Portney put the cost estimate f o r cleaning up a l l c i v i l i a n and m i l i t a r y hazardous waste s i t e s , including Resource Conservation and Recovery Act (RCRA) and Superfund mandates, at $420 b i l l i o n . Just one month l a t e r (10,2), t h i s estimate was raised to $750 b i l l i o n , with the t o t a l possibly surpassing $1 t r i l l i o n . Given that estimated costs of the average Superfund s i t e i s i n the range of $30-50 m i l l i o n (11), t h i s estimate should continue to increase rapidly as additional s i t e s are evaluated and added to the l i s t of hazardous waste s i t e s . The very alarming and rapid increase i n estimates of the cleanup cost results from a combination of (1) an increased recognition of the extent of contamination,(2) changes i n the regulations governing compliance that increase the cleanup "load" and specify more stringent standards, and (3) a growing recognition that we don't have a l l the answers and that technological breakthroughs are needed (12,IS). I t i s p r e c i s e l y t h i s trend i n cost that drives the need f o r both short and long-term research to develop new, improved and c o s t - e f f e c t i v e remediation technology. Laws and Regulations

Pertaining to Environmental Restoration

In preparing t h i s work, we found that one feature of the s o c i e t a l problems, the l e g a l feature, i s of preeminent importance i n d r i v i n g the economic and s c i e n t i f i c side of the remediation effort. However, relevant laws and regulations are not well understood even within the s c i e n t i f i c community. Treatment and disposal of hazardous waste, radioactive waste, and mixed waste are regulated by a myriad of statutes that address e x i s t i n g contamination problems, the management of e x i s t i n g waste, and the f i n a l disposal of t h i s and future waste generated. The most important of these, along with t h e i r i n t e r r e l a t i o n s h i p with various agencies, are shown i n Figure 1. The governing regulatory system i s complex and either d i r e c t l y or i n d i r e c t l y involves a number of applicable (1) federal and state statutes and local ordinances, (2) regulations promulgated by federal, state, and l o c a l agencies, (3) executive orders, and (4) agreements between the involved p a r t i e s . In t h i s section, i t i s our intent to give an overview of only the federal policies (5,14-20) that drive the regulation/remediation of hazardous and nuclear waste. This i s not to downplay the important, and often predominant, role played by the states and l o c a l i t i e s i n the o v e r a l l implementation of hazardous waste management. S t a t e - s p e c i f i c regulations are however largely based on federal law and are frequently more r e s t r i c t i v e than applicable federal regulations. Applicable regulations and

4

ENVIRONMENTAL REMEDIATION

AhhbClbD PARTIES

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

FEDERAL STATUTES

(^ROUNDWATER SOWA

RCRA HSWA

SARA NUCLEAR AEA NWPA

FEDERAL REGULATORS CEQ B>A DOE NRC

Figure 1. Regulations, statutes and agencies that define environmental restoration.

D e f i n i t i o n of Acronyms AEA - Atomic Energy Act CEQ - Council of Environmental Quality CERCLA - Comprehensive Environmental Response, Compensation & L i a b i l i t y Act CWA - Clean Water Act DOE - Department of Energy EPA - Environmental Protection Agency HSWA - Hazardous and Solid Waste Amendment ΝΕΡΑ - National Environmental Policy Act NRC - Nuclear Regulatory Commission NWPA - Nuclear Waste Policy Act RCRA - Resource Conservation and Recovery Act SARA - Superfund Amendments and Reauthorization Act SDWA - Safe Drinking Water Act SWDA - S o l i d Waste Disposal Act

1. REED IT AL.

Environmental Restoration and Separation Science5

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

s i t e - s p e c i f i c interpretations of decided on a case-by-case basis.

these

regulations

are usually

Regulation of Hazardous Waste. The first broad-reaching l e g i s l a t i o n that brought attention to environmental protection was the National Environmental Policy Act (ΝΕΡΑ - 1969). This act provided the basic national charter for environmental protection that recognized a balance between environmental protection and other factors important to national welfare. Its primary objectives were to (1) prevent environmental damage and (2) ensure that a l l government-agency decision making took environmental factors into account. New a c t i v i t i e s required the writing of environmental impact statements and, i n e f f e c t , made environmental protection the mandate of a l l government agencies. ΝΕΡΑ established the Council on Environmental Quality (CEQ) as the agency responsible for oversight of other federal agencies. The EPA was designated as a co-participant on t h i s council and has been empowered by subsequent l e g i s l a t i o n (primarily the Clean A i r Act - 1970) to act as the implementing arm of ΝΕΡΑ. EPA i s currently chartered to review the environmental impact statements of other agencies. Even with ΝΕΡΑ, i t was not u n t i l the mid 1970s that the problem of groundwater contamination/remediation began to receive a s i g n i f i c a n t amount of attention by the EPA. This occurred primarily due to the passage of three series of laws that related to (1) groundwater protection, (2) hazardous waste management, and (3) waste remediation. These acts combined to bring considerable attention to t h i s important problem of groundwater contamination and greatly increased the importance of managing hazardous wastes. The protection of groundwaters was first addressed i n the enactment of the Federal Water P o l l u t i o n Control Act (FWPCA) i n 1972. This brought groundwater controls under the j u r i s d i c t i o n of the federal government. This was amended to focus on the control of toxic pollutants i n groundwater and renamed the Clean Water Act (CWA) i n 1977. It has been further amended i n 1987 to tighten the discharge standards for toxic pollutants. This act currently provides the mechanism by which water q u a l i t y standards are established. Along the same lines of groundwater protection, the Safe Drinking Water Act (SDWA), passed i n 1974, provided for the safety of public water systems and required the EPA to set national drinking water standards. This was amended i n 1986 to quicken the pace of i t s implementation. The second series of l e g i s l a t i o n defined hazardous waste management. The S o l i d Waste Disposal Act (SWDA), enacted i n 1965, was the f i r s t act passed to regulate waste on a national scale. This was amended by the Resource Conservation and Recovery Act (RCRA), enacted i n 1976, and further amended by the Hazardous and S o l i d Waste Amendments (HSWA) of 1984. These acts c o l l e c t i v e l y provide "cradle to grave" regulation of hazardous waste. Included i n these acts are guidelines for management of s o l i d hazardous waste, provisions for strong federal enforcement of the regulations, a regulatory d e f i n i t i o n of hazardous waste (from which a p r i o r i t y pollutant l i s t was first derived) i n 40 CFR 261.2, a detailed regulatory strategy to address hazardous waste management, an i d e n t i f i c a t i o n of f i n a n c i a l r e s p o n s i b i l i t y for e x i s t i n g waste, and provisions to advance waste-management techniques.

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ENVIRONMENTAL REMEDIATION

The third series of acts, commonly referred to as CERCLA/superfund acts, provided the federal government with the authority to respond to ( i . e . , clean up) uncontrolled release of hazardous waste. The Comprehensive Environmental Response, Compensation, and L i a b i l i t y Act (CERCLA) was enacted i n 1977. CERCLA applies to the release or threat of release into the environment of any hazardous substance. The broad scope of t h i s statute i s indicated by the fact that "environmental" includes a l l environmental media, and "hazardous substance" i s broadly defined to include not only RCRA "hazardous waste" but a l i s t of substances i d e n t i f i e d by EPA i n 40 CFR 302, which now includes over 700 hazardous substances and over 1500 radionuclides. Whenever there i s a release or threat of a release of a hazardous substance to the environment, EPA i s authorized by the statute to undertake "removal" and/or "remedial" action. CERCLA was amended i n 1986 by the Superfund Amendments and Reauthorization Act (SARA). This changed the cleanup approach, increased the involvement of the public i n cleanup, and established a cleanup fund for superfund s i t e s . The enactment of CERCLA/SARA has spawned a number of related acts that address the n o t i f i c a t i o n of the affected community and response plans. The most important of these are the Emergency Planning and Community Right-To-Know Act (EPCRA) and the National Contingency Plan (NCP) enacted i n 1986 and 1990, respectively. Regulation o f Radioactive and Radioactive/Hazardous M i x e d Waste. The guidelines for the management of waste containing radioactive isotopes were established by the Atomic Energy Act (AEA). Under the provisions of t h i s act, commercial radioactive waste (e.g., spent nuclear f u e l and low-level radioactive medical waste) was regulated by the Nuclear Regulatory Commission and c o d i f i e d i n 10 CFR part 60 through 71. Radioactive waste generated by the defense industry, i n contrast, was regulated by DOE orders. DOE*s current environmental restoration p o l i c y i s to clean up contaminated f a c i l i t i e s and s i t e s within the weapons complex to achieve f u l l compliance with the l e t t e r and intent of the applicable federal, state, and l o c a l statutes (21). The Five Year Plan for Environmental Restoration and Waste Management (6) describes the technologies and research plans currently i d e n t i f i e d . Long-term research plans i n support of subsurface remediation (7) have also been published and are currently being implemented. Hazardous waste that contains radioactive material ( i . e . , mixed waste) i s regulated under both the AEA and RCRA. Under the AEA, the EPA has r e s p o n s i b i l i t y for s e t t i n g r a d i a t i o n protection standards, which are implemented through DOE orders, e.g., Order 5820.2A for DOE radioactive materials (22). This dual regulation further complicates environmental restoration a c t i v i t i e s that involve mixed waste. Regulatory Approach t o S i t e Remediation. Most environmental cleanup standards are derived from the provisions of CERCLA, section 121 "Cleanup Standards" or RCRA, S u b t i t l e C e n t i t l e d "Hazardous Waste Management." The implementing regulations are

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1. REED ET AL.

Environmental Restoration and Separation Science7

found, respectively, i n 40 CFR part 300 and i n 40 CFR parts 264, 265, and 268. Although CERCLA i s intended to deal with cleanup of past environmental problems and RCRA i s largely intended t o prevent future contamination, both statutes and t h e i r implementing regulations can affect environmental restoration. Although the p r i n c i p a l statutes and regulations that apply to environmental restoration a c t i v i t i e s are c i t e d above, standards that derive from other environmental statutes such as CWA, SDWA, ΝΕΡΑ, and state laws s t i l l apply. In general, state standards may be substituted f o r federal standards when the state standards impose requirements that are at least as stringent as the federal standards. Detailed information on the statutes and the associated implementing regulations can be obtained from the "Environmental Guidance Program Reference Books" prepared by Oak Ridge National Laboratory (16). In addition, an overview of the system of environmental statutes and regulations that govern environmental restoration can be obtained from the reference books "Environmental Law Handbook," "Environmental Statutes," and "State Environmental Law Handbooks" published by Government I n s t i t u t e s , Inc. (17-19). The NCP contains several c r i t e r i a that are intended to guide decisions on the standards to be achieved i n i n d i v i d u a l remedial actions. Among these the most important are the "threshold c r i t e r i a , " which include (1) a general requirement to protect human health and the environment and (2) cleanup standards which have applicable or relevant and appropriate requirements (ARAR). Under the ARAR approach, EPA can use standards from other federal and state statutes (e.g., CWA, SDWA, RCRA) on a case-by-case basis when these requirements are "applicable or relevant and appropriate." For example, RCRA land-disposal restorations (LDR) may be "relevant and applicable" i f a CERCLA remedial action involves RCRA hazardous waste and the waste or i t s hazardous residue i s to be land disposed. In t h i s case, the RCRA LDR standards that are based on the best demonstrated available technology (BDAT) may apply. Environmental restoration a c t i v i t i e s may be conducted under a RCRA, Part Β permit when RCRA hazardous wastes are involved. The RCRA hazardous wastes are i d e n t i f i e d i n 40 CFR 261 and include " c h a r a c t e r i s t i c " hazardous wastes as defined i n subpart C and " l i s t e d " hazardous wastes as defined i n subpart D. The Hazardous and S o l i d Waste Amendment (HSWA) to RCRA includes prohibitions on land disposal of hazardous waste. Under t h i s statute, the EPA has issued regulations (40 CFR 286) that ban the land disposal of untreated hazardous waste and has established treatment standards based on the BDAT. The way that these standards can be involved i n a CERCLA remedial action was discussed above. In addition, technical standards f o r environmental restoration a c t i v i t i e s conducted under a RCRA, Part Β permit are given i n 40 CFR 264, including closure requirements and groundwater concentration l i m i t s (see 40 CFR 264.94). Organic and Metal Restoration

Pollutants

of Importance

t o Environmental

The l i s t of metals, radionuclides, and organic compounds that are now recognized as environmental pollutants continues to grow. The

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ENVIRONMENTAL REMEDIATION

l i s t of 129 p r i o r i t y pollutants i d e n t i f i e d i n RCRA o r i g i n a l l y included 13 metals, with the remainder being organic compounds. When DOE s i t e s are also considered, an additional several hundred radioisotopes are added to t h i s l i s t . The l i s t of organics has grown; over 1000 are now subject to reporting requirements. Any of the estimated 500,000 organics currently i n use have the p o t e n t i a l to be designated as a hazardous material. Numerous l i s t s of p r i o r i t y pollutants e x i s t . It i s important to note that both concentration limits and the l i s t of p r i o r i t y / r e g u l a t e d contaminants are undergoing constant review and are often superseded by l o c a l and state regulations. In t h i s context, we have not t r i e d to tabulate a comprehensive l i s t i n t h i s section. Rather, i t i s our objective to simply i d e n t i f y some of the more important contaminants. This i s important from the perspective of determining the proper emphasis i n the development of separations technology. Regulatory D e f i n i t i o n of Hazardous, Radioactive, and Mixed Waste. E x i s t i n g federal regulations give s p e c i f i c regulatory d e f i n i t i o n s for a l l waste types. Wastes that are of most i n t e r e s t to environmental restoration and waste management are! hazardous waste, radioactive waste, and mixed waste. Hazardous waste i s defined i n 40 CFR part 261.3 as s o l i d waste (as defined i n 40 CFR part 261.2) that (1) i s not excluded from regulation as a hazardous waste under section 262.4 and (2) could cause or s i g n i f i c a n t l y contribute to an increase i n mortality or an increase i n serious i r r e v e r s i b l e or incapacitating r e v e r s i b l e i l l n e s s , or (3) could pose a substantial present or p o t e n t i a l hazard to human health and/or the environment when improperly stored or treated. Materials that are not s o l i d waste and, hence, not subject to regulation as hazardous waste are domestic sewage, i n d u s t r i a l wastewater that q u a l i f i e s as point-source discharges (section 402 of the Clean Water Act as amended), i r r i g a t i o n return flows, nuclear material as defined by the Atomic Energy Act of 1954 (42 U.S.C. 2011 amendment), materials subjected to i n s i t u mining techniques, pulping l i q u o r s , spent s u l f u r i c acid, reclaimed secondary materials, spent wood preserving s o l u t i o n , and the byproducts of producing coke and coal tar i n the s t e e l industry. A d d i t i o n a l l y , a l l s o l i d waste i s not hazardous waste. S o l i d waste excluded are household waste, s o l i d waste generated i n farming and r a i s i n g animals, mining overburden returned to the mine s i t e , waste generated primarily from the combustion of coal and fossil fuels, drilling fluids/wastes associated with oil/gas/geothermal d r i l l i n g , chromium-containing waste i f the waste generator can demonstrate that it will fail the toxicity characteristic. Operationally, a waste i s c l a s s i f i e d as hazardous based on three c r i t e r i a : (1) i t i s l i s t e d as a hazardous waste (40 CFR 261 subpart D); (2) i t has one of the following four c h a r a c t e r i s t i c s : i g n i t a b i l i t y , c o r r o s i v i t y , r e a c t i v i t y , and t o x i c i t y (see 40 CFR 261 subpart C for the s p e c i f i c d e f i n i t i o n of these c h a r a c t e r i s t i c s ) ; or (3) i t f a l l s into the category of "other" hazardous waste (primarily mixtures of non-hazardous materials with hazardous waste).

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

1. REED ET AL.

Environmental Restoration and Separation Science9

The second type of waste i s radioactive waste. This i s nonhazardous waste that i s categorized primarily according to transuranic content and o r i g i n into three c l a s s i f i c a t i o n s : lowl e v e l waste, transuranic (TRU) waste, and high-level waste (HLW). Low-level and TRU waste are defined i n DOE order 5820.2A (see section II.3a). Low l e v e l waste i s radioactive waste that contains less than 100 nCi/g of waste of alpha-emitting transuranics with a >20 year h a l f - l i f e . TRU waste i s radioactive waste that (1) i s not high-level waste and (2) has a s p e c i f i c a c t i v i t y of >100 nCi/g of waste containing transuranic, long-lived alpha emitters. Highl e v e l waste i s defined i n 10 CFR part 60.2 as either (1) i r r a d i a t e d reactor f u e l , (2) l i q u i d waste generated from the f i r s t cycle of solvent extraction i n the processing of nuclear f u e l and subsequent concentrates, or (3) s o l i d s into which such l i q u i d s have been converted. There i s a growing recognition that much of the radioactive waste at DOE s i t e s (7,BS) co-exists with hazardous waste that i s primarily organic i n nature. Waste that contains both radioactive and RCRA-defined hazardous components i s c l a s s i f i e d as mixed waste. This type of waste i s subject to both RCRA and DOE/NRC c o n t r o l , whichever i s the more stringent. Metal Contaminants i n the Environment. From the perspective of environmental remediation, the focus of separation science should be on the metals currently being regulated from the standpoint of groundwater protection. This i s not a hard and fast r u l e , as there are a number of situations (e.g., s p e c i f i c s p i l l s , waste-streams p e c i f i c toxins, etc.) where the focus w i l l be on the removal of a s p e c i f i c hazardous metal compound or substance for which standards have not been set. For example, there i s currently much emphasis within the DOE on uranium contamination at the Fernald S i t e i n Ohio. The metals (excluding radionuclides) currently i d e n t i f i e d for regulation under RCRA/SDWA are l i s t e d i n Table I. The o r i g i n a l l i s t of 13 metals was defined i n the 1986 r e v i s i o n of the SDWA. These include two group II metals (barium and beryllium), eight t r a n s i t i o n metals (cadmium, chromium, copper, lead, mercury, n i c k e l , s i l v e r , and thallium), and three near-transition metals (selenium, arsenic, and antimony). The maximum concentration l i m i t s i n Table I are currently under review, and lower l i m i t s have already been proposed for some metals. In addition to t h i s change, an additional s i x metals have been proposed for consideration. These, as of the January 1991 r e v i s i o n , are aluminum, manganese, molybdenum, strontium, vanadium, and zinc. Promulgation of t h i s l i s t i s i n progress, with groundwater protection guidelines expected to be established i n the near future. The importance of the maximum concentration l i m i t s established to protect groundwaters i n assessing the need for remediation i s not e n t i r e l y c l e a r . CERCLA/superfund cleanup a c t i v i t i e s are not required to achieve these defined groundwater protection l i m i t s . Other factors, such as a v a i l a b i l i t y of technology, background groundwater l e v e l s , and r i s k to health, also need to be considered. The trend, however, appears to be i n the d i r e c t i o n of using the groundwater protection l i m i t s as the target and standard for environmental restoration.

ENVIRONMENTAL REMEDIATION

10

Metals Listed under RCRA/SDWA as P r i o r i t y Pollutants

Table I.

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

Metals

a

Toxicity L i m i t s (mg/L)

Arsenic Barium Cadmium Chromium Lead Mercury Selenium Silver Antimony Beryllium Copper Nickel Thallium

EPA G u i d e l i n e s (/Ig/L)

b

0

5

5.0 100 1.0 5.0 5.0 0.2 1.0 5.0

10 100 50 2

6 4 1300 100 2

a

0 r i g i n a l l i s t proposed i n the 1986 amendment to the Safe Drinking Water Act. ^Maximum concentration l i m i t s currently defined i n 40 CFR part 261.24 based on the t o x i c i t y c r i t e r i o n . Reference 23, Table 7 and "Drinking Water Limits Set for 23 More Compounds," Chem. Eng. News, 1992, 10(14)» 19. c

Radionuclides i n the Environment. The 1986 amendment of SDWA also addressed the presence of radionuclides i n groundwater from the perspective of r a d i o t o x i c i t y . Table II l i s t s radionuclides currently regulated under EPA/DOE guidelines.

Table I I .

Radioisotopes Currently Regulated under E P A / D O E Guidelines

Concentration Guideline

Radionuclide

Beta p a r t i c l e and photon radioactivity Gross alpha p a r t i c l e a c t i v i t y 0

Radium-226 and -228 Uranium^ Strontium* Plutonium** Cesium 5

b

a

a

0

Re ference 24, based on dose-to-man of 100 mRem/year calculations s p e c i f i c to the Hanford s i t e .

1. REED ET AL.

Environmental Restoration and Separation Science 11

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

Radium and uranium» are associated with the mining and/or presence of uranium deposits i n the subsurface. Regulations pertaining to these are found i n 40 CFR part 192. The other radionuclides are associated with nuclear waste. Groundwater contamination l i m i t s for these are defined by dose-to-man calculations from the perspective of r a d i o t o x i c i t y . There are no isotope or r a d i o n u c l i d e - s p e c i f i c concentration standards for the transuranics from the perspective of t o x i c i t y . By inventory, the following are the radioactive metals that are of most concern: Strontium-90 Technetium-99 Tin-126 Cesium-135, -137 Radium-226 Thorium-230, -232 Uranium-233, -234, -235, -236, -238 Neptunium-237 Plutonium-238, -239, -240, -242 All are long-lived radionuclides and are currently receiving attention, to varying extents, within the DOE as subsurface contaminants that may require remediation. Some of these isotopes appear as both toxic and radiotoxic pollutants. In t h i s event, the more stringent c r i t e r i o n applies. The vast majority of groundwater and subsurface media contaminated with radionuclides are at s i t e s associated with DOE f a c i l i t i e s . Although numerous s i t e - s p e c i f i c reports e x i s t , i t has only been recently that a general study of the levels of contamination at a l l DOE s i t e s was made by Zachara and R i l e y (23). The major observations of t h i s study are the predominance of organics and radionuclide mixtures at e x i s t i n g DOE waste s i t e s . The most important radionuclides i d e n t i f i e d , based on frequency of appearance i n reported analytical r e s u l t s , were plutonium, amerlcium, uranium, neptunium, and cobalt. Organic Species i n the Environment. The predominance of organic species as contaminants i n subsurface media i s r e a d i l y recognized (25-30), They have been described as "the most common healththreatening chemicals detected i n groundwater," and the greatest d i f f i c u l t i e s i n groundwater remediation have been encountered at organic contamination s i t e s (25). The s c i e n t i f i c and technological problems posed by organic contamination range from microscopic considerations, such as the actual d i f f i c u l t y of bringing about a separation or transformation of a given pollutant i n a given environment, to macroscopic considerations such as the huge costs, volumes, and range of materials involved. S p e c i f i c l i s t s that i d e n t i f y p r i o r i t y pollutants have been established. The l i s t of regulated organics (SDWA, 1986) i s given i n Table I I I . This l i s t includes 14 v o l a t i l e organics (primarily halogenated hydrocarbons and benzene), 5 microbial species, and 41 non-volatile organics (pesticides and higher molecular weight solvents). The SDWA p r i o r i t y l i s t for future consideration includes an additional 19 pesticides and 43 synthetic organics.

12

ENVIRONMENTAL REMEDIATION

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

RCRA-related controls exist on over 1000 organic species. Approximately 200 of these are currently l i s t e d as acutely hazardous waste, with an additional 350 l i s t e d as hazardous waste. A t o t a l of 250 organics have been i d e n t i f i e d f o r consideration i n establishing groundwater monitoring p r i o r i t y l i s t s (Appendix IX constituents). Groundwater standards are t y p i c a l l y i n the low fig/L range (e.g., 5 μg/L f o r dichloromethane, 2 μg/L for Endrin, 20 μg/L for diquat and 1 μg/L for hexachlorobenzene).

Table I I I . Organic Contaminants Required t o Be Regulated under the SDWA of 1986 V o l a t i l e Organics Trichloroethylene Tetrachloroethylene Carbon tetrachloride 1,1,1-Trichloroethane 1,2-Dichloroethane V i n y l chloride Methylene chloride

Benzene Chlorobenzene Dichlorobenzene Trichlorobenzene 1,1-Dichloroethylene Trans-1,2-Dichloroethylene Cis-1,2-Dichloroethylene

Microbiology and Turbidity Total coliforms Turbidity Giardia lamblla

Viruses Standard plate count Legionella Organics 1,1,2-Trichloroethane Vydate Simazine PAHs PCBs Atrazlne Phthalates Acrylamide Dibromochloropropane (DBCP) 1,2-Dichloropropane Pentachlorophenol Pichloram, Dinoseb Ethylene dibromide (EDB)

Endrin Lindane Methoxychlor Toxaphene 2,4-D 2,4,5-TP Aldicarb Chlordane Dalapon Diquat Endothall Glyphosate Carbofuran Alachlor Epichlorohydrin Toluene Adipates 2,3,7,8-TCDD(Dioxin) Aldicarb sulfone Aldicarb sulfoxide Ethybenzene Heptachlor Heptachlor expoxide Styrene

Xylene Hexachlorocyclopentadiene

SOURCE : Keith, L. H.; T e l l i a r d , W. Α., Environ. TechnoL.

, 1979, 18(4),

416.

Sex.

1. REED ET AL.

13 Environmental Restoration and Separation Science

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

Issues Associated with Environment Restoration There are a number of issues associated with remediation of contaminated s i t e s that are currently under debate i n the t e c h n i c a l community. The most important of these, the i m p r a c t i c a l i t y of t o t a l remediation, was stated as early as 1980 by the U.S. Geological Survey (SI) i n the following way: "deterioration i n [groundwater] quality constitutes a permanent loss of water resource because treatment of the water or r e h a b i l i t a t i o n of the aquifers i s presently generally impractical." This point has been re-stated i n more recent commentaries (2,12, IS), and the issues of f e a s i b i l i t y , cost, contaminant, prioritization, and o v e r a l l approach to remediation remain. This important debate w i l l continue as more i s learned about both the l i m i t a t i o n s and successes of remediation technology. Although the l i s t of s p e c i f i c issues i s long, a few general issues become clear when the many factors associated with groundwater remediation are considered. The most important of these are: Existing Contaminated Sites •

Complete and total remediation of a l l existing groundwater, although a laudable goal, i s not r e a l i s t i c . This i s due to the enormity of the problem, the l i m i t e d resources available for the task, and i n many instances, the absence of suitable and r e l i a b l e technology to treat the problem to the extent s p e c i f i e d by e x i s t i n g regulations.

•

I t i s important to p r i o r i t i z e e x i s t i n g groundwater problems i n terms of health r i s k / b e n e f i t . This i s a complex issue that includes re-examination of the regulations that drive and define remediation and reinterpretation of the guidelines i n terms of cost and general r i s k .

•

Improved characterization and detection methodology i s needed. The vast majority of monitoring i s s t i l l done by variations on water sampling combined with extensive analysis. Early detection of problems and early detection technology at new waste disposal s i t e s can greatly reduce the extent of contamination.

Future Waste Generated •

Improved waste minimization, documentation, and handling are needed. This i s self-evident, with numerous examples of "past s i n s " i n the l i t e r a t u r e when t h i s was not done.

•

Long-term solutions that meet regulatory c r i t e r i a are needed for waste storage. There are currently no

14

ENVIRONMENTAL REMEDIATION

licensed f a c i l i t i e s for the long-term disposal of hazardous mixed waste, high-level nuclear waste, or transuranic waste.

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

Role of Separation Science i n Environment Restoration Treatments available to environmental remediation f a l l into three broad categories. These are transformation (i.e., destruction), separation, and immobilization. While destruction and immobilization are ends i n and of themselves, separation i s not. In f a c t , separation only makes sense i f i t aids i n a t t a i n i n g one or both of these more permanent solutions. For example, destruction of a hydrocarbon by i n c i n e r a t i o n i s feasible i f i t existed as a 10 wt % aqueous sludge rather than a 100 ppb aqueous solution. F i n a l disposal of 10 kg of plutonium would be less costly and more c e r t a i n than the cleanup of an equivalent amount of plutonium i n 10^ kg of plutonium-contaminated s o i l . A successful separation process should have two products: a low-volume stream containing the contaminant(s) i n a concentrated form and a high-volume stream containing the decontaminated matrix. In general, the concentration of the contaminant(s) i s the easier task. Achieving regulated concentration l i m i t s often c a l l s for very high decontamination levels in the larger-volume, decontaminated product. This, i n some cases, necessitates the removal of 99.9999% of the contaminant. Also, process design requirements for concentrating the contaminant(s) and decontaminating the matrix are generally i n opposition, and a compromise i s struck between these two goals. Because a separation i s not an end i n i t s e l f , the benefits ( i . e . , goals) of a s p e c i f i c separation are c l e a r l y defined by the d i s p o s i t i o n of i t s product streams. Based on the old adage, "a s t i t c h i n time saves nine," waste avoidance i s an area where separations can be of great benefit to the environment. The use of separation technologies to reclaim/recycle materials has become a very important area i n environment restoration, and zero discharge i s quickly becoming the goal of a l l waste producers. As the cost of the disposal of hazardous waste increases, industry has come to recognize that recycle, once more of a public relations e f f o r t , i s now an economic necessity. L a s t l y , the extremely important role of separations i n the analysis of environmental samples should not be overlooked. The interplay of t e c h n i c a l , s o c i e t a l , and l e g a l factors has driven the lower l i m i t s of d e t e c t a b i l i t y and concern to ever decreasing concentrations. The many separations challenges that exist i n t h i s area have been previously noted i n government reports (6, Ύ, SB). Assessment of Available Technology. The v i t a l role of separations and the incentives i n probing i t s f r o n t i e r s have been w e l l recognized at the national l e v e l by two reports i n recent years (SB,S3)* Although few references focus on separations per se, there are i n the l i t e r a t u r e numerous on the whole range of remediation technologies (30,34-41). In addition to t h i s , an excellent source of information i s the l i t e r a t u r e from the EPA (42,43).

1. REED ET AX.

Environmental Restoration and Separation Science 15

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

In a compendium of technologies used i n the treatment of hazardous waste (42), technologies are categorized into physical treatment, chemical treatment, b i o l o g i c a l processes, thermal destruction, and f i x a t i o n / s t a b i l i z a t i o n processes. Separation technologies are contained e n t i r e l y within the physical treatment processes section. Those technologies addressed are: • • • • • • • • •

sedimentation centrifugation flocculation oil/water separation dissolved a i r f l o t a t i o n heavy media separation evaporation a i r stripping steam s t r i p p i n g

• • • • • • • • • •

distillation s o i l flushing/washing chelation l i q u i d / l i q u i d extraction s u p e r c r i t i c a l extraction filtration carbon adsorption reverse osmosis ion exchange electrodialysis

In a c o l l e c t i o n of synopses of federal demonstrations of innovative s i t e remediation technologies (4s), technologies are categorized into bioremediatlon, chemical treatment, thermal t r e a t ment, vapor extraction, s o i l washing, s o l i d i f i c a t i o n / s t a b i l i z a t i o n , and other physical treatments. Here separation technologies are contained i n the thermal treatment, vapor extraction, s o i l washing, and other physical treatment sections. Key technologies addressed are : • • • • • • • • • • • • • • • • • • • • • • • • • •

desorption and vapor extraction low-temperature thermal stripping low-temperature thermal treatment radiofrequency thermal s o i l decontamination X*TRAX low-temperature thermal desorption groundwater vapor recovery system i n s i t u s t r i p p i n g with horizontal wells i n s i t u s o i l venting i n s i t u steam/air stripping integrated vapor extraction and steam vacuum s t r i p p i n g Terra Vac i n s i t u vacuum extraction vacuum induced s o i l venting BEST solvent extraction Biogenesis s o i l cleaning system B i o t r o l s o i l washing system debris washing system Ghea Associates process s o i l treatment with Extraksol solvent extraction Carver-Greenfield process f o r extraction of o i l y waste Chemtect gaseous waste treatment freeze separation membrane m i c r o f i l t r a t i o n p r e c i p i t a t i o n , m i c r o f i l t r a t i o n , and sludge dewatering rotary a i r s t r i p p i n g ultrafiltration

16

ENVIRONMENTAL REMEDIATION

A number of these technologies are represented i n the contributions to the symposium proceedings that follow t h i s introductory chapter. As reflected i n these contributions, there are clear benefits to almost a l l of these technologies when a suitable environmental restoration problem e x i s t s .

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

Conclusions and Recommendations The estimated costs of environmental remediation are huge. Regulatory constraints and interpretations are constantly evolving. The technical challenges are staggering. Innovative separation technologies are needed that are economical, acceptable to the public, and e f f e c t i v e . In developing new separations for environmental remediation or waste avoidance, i t i s important to never disconnect the separation operation from the goals of the entire process. These are; • • •

Decontamination of the bulk of the groundwater, s o i l , or waste stream Concentration of the contaminant(s) Assured and economic f i n a l disposal or recycle of the contaminant(s)

Separation i s not an end i n i t s e l f but a means to an end. The d i s p o s i t i o n of a l l effluents must be accounted f o r , and f i n a l disposal of equipment must be planned. In general, the products of waste treatment of environmental remediation have no value, and the governing c r i t e r i a i n successful treatment i s cost minimization. The separation that produces the least expensive disposal of products at the lowest processing cost i s the best process. S o c i a l and regulatory pressures w i l l continue to govern what the most important problems are; economics w i l l continue to drive the choices i n treatments and long-term research emphasis. Work supported by the U.S. Department of Energy under Contract W-31-109-Eng-38. L i t e r a t u r e Cited 1.

2. 3.

4.

5. 6.

"Evaluation of Groundwater Extraction Remedies," O f f i c e of Solid Waste and Engineering Response, United States Environmental Protection Agency, Washington DC, 1989, EPA/540/2-89/054. Abelson, P. Η., "Remediation of Hazardous Waste S i t e s , " S c i . , 1992, 255, 901. "The Eighteenth and Nineteenth Annual Report of the Council on Environmental Quality together with the President's Message to Congress," Council on Environmental Quality, U.S. Department of Commerce, N.T.I.S., 1989, PB90-163148. "Characterization of Municipal S o l i d Waste i n the United States, 1960 to 2000 (Update 1988)," Franklin Associates Ltd., U.S. Environmental Protection Agency, Office of S o l i d Waste, 1988, c i t e d i n reference 3, p. 42. Cooke, S. Μ., The Law of Hazardous Waste; Mathew Bender and Co. Inc.: New York, NY, 1991; Vol. 1-3. "Environmental Restoration and Waste Management - Five Year Plan, F i s c a l Years 1993 - 1997," U.S. Department of Energy, Washington, DC, 1991, FYP DOE/S-0089P.

1. REED ET AL.

Environmental Restoration and Separation Science 17

"Evaluation of Mid-to Long Term Basic Research f o r Environmental Restoration," O f f i c e of Energy Research, U.S. Department of Energy, Washington, DC, 1989, DOE/ER-419. 8. "DOE LDR Strategy Report f o r RMW," U.S. Department of Energy, Washington, DC, 1989, DOE/EH-91002927. 9. Portney, P., Report prepared f o r Resources for the Future, Washington, DC, c i t e d i n Tox. Mat. News, 1991, 18(45), 446. 10. Russell, Μ., "Hazardous Waste Remediation: The Task at Hand," Report f o r The Waste Management Research and Education I n s t i t u t e , The University of Tennessee, Knoxville, TN. Cited Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

7.

i n Tox. Mat. News,

1991, 18(50),

493.

11. Cooke, S. Μ., The Law of Hazardous Waste; Mathew Bender and Co.: Inc., New York, NY, 1991; V o l . 1, pp. i v . 12. Rowe, J r . , W. D., "Superfund and Groundwater Remediation: Another Perspective,"

13. Travis, C.; Doty, C.

Environ.

Sci.

Technol.,

1991, 25(3),

370.

"Commentary on Groundwater Remediation at

Superfund S i t e s , " Environ.

Sci.

1990, 24(10),

Technol.,

1464.

14. Wright, A. P.; Coates, Η. Α., "Legislative I n i t i a t i v e s f o r S t a b i l i z a t i o n / S o l i d i f i c a t i o n of Hazardous Wastes," Toxic and Hazardous Waste Disposal; Ann Arbor Science Publishers Inc.: Ann Arbor, MI, 1979; Vol. 2, Chapter 1. 15. Wagner, T.

16. 17. 18. 19.

20. 21. 22. 23.

24.

25.

P.,

The

Complete

Guide

to

The

Hazardous

Waste

Regulations; Second Edition; Van Nostrand Reinhold: New York, NY, 1991. "Environmental Guidance Program Reference Books," Oak Ridge National Laboratory, Oak Ridge, TN, 1990, ORNL/M-1277. Environmental Law Handbook; Eleventh e d i t i o n ; Government I n s t i t u t e s , Inc.: Rockville, MD, 1991. Environmental Statutes; Eleventh edition; Government I n s t i t u t e s , Inc.: Rockville, MD, 1991. "State Environmental Law Handbooks," These are s t a t e - s p e c i f i c handbooks on environmental law. Information on these can be obtained by c a l l i n g (301) 251-9250. ΝΕΡΑ Deskbook, Environmental Law I n s t i t u t e : Washington, DC, 1989. EPA Register Notice, July 3, 1986. Interpreted by the DOE i n 1987. "DOE order 5820.2a," U.S. Department of Energy, Washington, DC, 1988. Riley, R. G.; Zachara, J . Μ., "Nature of Chemical Contaminants on DOE Lands and I d e n t i f i c a t i o n of Representative Contaminant Mixtures for Basic Subsurface Science Research," O f f i c e of Energy Research, U.S. Department of Energy, Washington, DC, 1992, DOE/ER-0547T. R. E. Jacquish and R. W. Bryce, "DOE derived Concentration guides based on e f f e c t i v e dose l i m i t not t o exceed 100 millirem/year." Derived from DOE Order 5480.1A: in "Hanford S i t e Environmental; Report f o r Calendar Year 1989" P a c i f i c Northwest Laboratory, Richland, WA, 1990, PNL-7346. Mackay, D. M.; Cherry, J . Α., "Groundwater Contamination: Pump-and-Treat Remediation," Environ. S c i . Technol., 1989, 23, 630.

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18

ENVIRONMENTAL REMEDIATION

26. Mackay, D. M.; Roberts, P. V.; Cherry, J. Α., "Transport of Organic Contaminents i n Groundwater," Environ. Sci. Technol., 1985, 19, 384. 27. McCarty, P. L.; Reinhard, M.; Rittmann, Β. Ε., "Trace Organics i n Groundwater," Environ. Sci. Technol., 1981, 15, 41. 28. Mongan, T. R., " P r i o r i t y Pollutant C r i t e r i a and the Clean Water Act," Wat. Env. Tech, 1991, December, 38. 29. Perry, A. S.; Muszkat, L.; Perry, R. Υ., " P o l l u t i o n Hazards from Toxic Organic Chemicals," i n "Toxic Organic Chemicals i n Porous Media," Eds: Z. G e r s t l , Y. Chen, U. M i n g l e l g r i n , B. Yaron, Springer-Verlag, B e r l i n , New York, 1989. 30. Heilshorn, E. D., "Removing VOCs from Contaminated Water," Chem. Eng.,

1991,

98,

152.

31. Meyer, G., "Groundwater Contamination - No 'Quick Fix' i n Sight," USGS yearbook; U.S. Geological Survey: Washington DC, 1980. 32. "Opportunities i n Chemistry," Report of the Committee to Survey Opportunities i n the Chemical Sciences, United States National Research Council, National Academy Press, Washington, DC, 1985. 33. "Frontiers i n Chemical Engineering: Research Needs and Opportunities," Report of the Committee on Chemical Engineering F r o n t i e r s : Research Needs and Opportunities, United States National Research Council, National Academy Press, Washington, DC, 1988. 34. Z i e g l e r , G. J . , "Remediation Through Groundwater Recovery and Treatment," Poll. Eng., 1989, July, 75. 35. "USEPA T r e a t a b i l i t y Manual: Volume I I I . Technologies f o r Control/Removal of Pollutants," Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, 1983, EPA-600/2-82/001a. 36. O ' N e i l l , E. J . , "Working to Increase the Use of Innovative Cleanup Technologies," Wat. Env. Tech., 1991, December, 48. 37. Dworkin, D.; Cawley, Μ., "Aquifer Restoration: Chlorinated Organics Removal Considerations i n Proven vs. Innovative Technology," Env. Prog., 1988, 7, 99. 38. Cheremisinoff, P. Ν., "Water and Wastewater Treatment Fundamentals and Innovations," Poll. Eng., 1989, March, 94. 39. Hauck, J . ; Masoomian, S., "Alternative Technologies for Wastewater Treatment," Poll. Eng., 1990, May, 81. 40. Eaton, D. L.; Smith, T. H.; Clements, T. L.; Hodge, V., "Issues i n Radioactive Mixed Waste Compliance with RCRA: Some Examples from Ongoing Operations at the Idaho National Engineering Laboratory," Idaho National Engineering Laboratory, Idaho F a l l s , ID, 1990, EGG-M-89352. 41. McGlochlin, S. C.; Harder, R. V.; Jensen, R. T.; P e t t i s , S. A.; Roggenthen, D. Κ., "Evaluation of Prospective Hazardous Waste Treatment Technologies for Use i n Processing Low-Level Mixed Wastes at Rocky F l a t s , " EG&G Rocky F l a t s , Inc., Rocky F l a t s Plant, Golden, CO, 1990, RFP-4264.

1. REED ET AL.

Environmental Restoration and Separation Science 19

42. "A Compendium of Technologies Used i n the Treatment of Hazardous Waste," Center for Environmental Research Information, United States Environmental Protection Agency, C i n c i n n a t i , OH, 1987, EPA/625/8-87/014. 43. "Synopses of Federal Demonstrations of Innovative S i t e Remediation Technologies," Center for Environmental Research Information, United States Environmental Protection Agency, C i n c i n n a t i , OH, 1991, EPA/540/8-91/009.

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch001

RECEIVED June 29, 1992

Chapter 2

Removal of Inorganic Contaminants from Groundwater Use

of Supported Liquid Membranes 1,3

1

2

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

R. Chiarizia , E. P. Horwitz , and Κ. M . Hodgson

1Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 2Westinghouse Hanford Company, P.O. Box 1970, Richland, WA 99352 This review paper summarizes the results of an investigation on the use of supported liquid membranes for the removal of uranium(VI) and some anionic contaminants (technetium(VII), chromium(VI) and nitrates) from the Hanford site groundwater. As a membrane carrier for U(VI), bis(2,4,4-trimethylpentyl)phosphinic acid was selected because of its high selectivity over calcium and magnesium. The water soluble complexing agent 1-hydroxyethane-l,l-diphosphonic acid was used as stripping agent. For the anionic contaminants the long-chain aliphatic amines Primene JM-T (primary), Amberlite LA2 (secondary) and trilaurylamine (tertiary) were investigated as membrane carriers. Among these amines, Amberlite LA-2 proved to be the most effective carrier for the simultaneous removal of the investigated anion contaminants. A good long-term stability (at least one month) of the liquid membranes was obtained, especially in the uranium(VI) removal.

A supported liquid membrane (SLM) process has been considered, among other possible options, for the removal of contaminants from groundwater, because of the following advantages of SLM's over competing techniques (solvent extraction, ion exchange, polymeric membrane processes, etc.): 1. 2. 3. 4.

high concentration factors achieved through a high feed to strip volume ratio low carrier inventory required no phase separation problems negligible organic phase entrainment in the feed and strip aqueous phases (although loss of organic phase due to solubility is still inevitable) 5. simplicity of operation of membrane modules.

These advantages, however, are balanced by typical drawbacks of SLM processes, such as the lack of a scrub stage, which makes more stringent the need of a high 3

On leave from the Italian Nuclear and Alternative Energy Agency, ENEA, Rome, Italy

0097-6156/92/0509-0022$06.00/0 © 1992 American Chemical Society

2.

CHIARIZIA ET AL.

Removal of Inorganic Contaminants from Groundwater

selectivity, and the lack of long-term stability, which allows for a practical application. With these considerations in mind, we have performed an investigation on the use of S L M s to remove selected contaminants from the Hanford site groundwater, as an application of the basic knowledge previously acquired at the Chemistry Division of Argonne National Laboratory (1-4). The detailed results of this investigation have been the subject of a number of publications (5-S). In the present paper we review the most important results and conclusions.

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

Groundwater The detailed analysis of the Hanford groundwater has been reported in ref. (6). In Table I we report the typical concentrations of the species relevant for our investigation. Table I. Concentration of Selected Contaminants in Hanford Groundwater Contaminant Concentration MCL low high (maximum contaminant limit) 45 nitrate (ppm) 1,460 46 50 chromate (ppb) 437 51 900 ^Technetium 29,100 906 (picoCi/L) 10 Uranium (ppb) 8.590 SOURCE : Adapted from ref. (7). To perform our SLM experiments, a synthetic groundwater solution (SGW), simulating the composition of the groundwater from a specific Hanford monitoring well, was prepared using the procedure reported in ref. (5). The composition of the SGW is reported in Table II. The pH of the SGW was adjusted to 2 with H2SO4 for reasons that will be discussed later. For distribution and/or permeation experiments, the SGW was spiked with U-233, or Tc-99, cm- made 10" M with Na2Cr04. From Table II it appears that, apart from sodium, the major cationic constitutents of SGW are calcium and magnesium. Any method devised to remove uranium from the solution, must therefore exhibit a very high selectivity over these two components. Similarly, a good selectivity for nitrates over sulfatebisulfate species is required.

3

Table II. Composition of Synthetic Groundwater at D H 2 Molarity Constituent 0.012 Calcium Magnesium 0.0062 Sodium 0.017 Silicon 0.0009 Chloride 0.0016 Sulfate-bisulfate 0.017 Nitrate 0.030 Uranium 0.0004 Sum of Molarities 0.094 SOURCE: Reprinted with permission from ref. (5). Copyright 1990.

24

ENVIRONMENTAL REMEDIATION

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

Membrane Supports The liquid membrane suppôts were used both in flat-sheet and hollow-fiber configurations. In the flat-sheet membrane experiments Celgard or Accurel polypropylene membranes were used, with a thickness ranging from 25 to 100 microns, a pore size from 0.02 to 0.1 microns, and a porosity from 38 to 75%. The hollow-fibers were obtained from Enka. They were also made of propylene, with a porosity of 75%, a pore size of 0.1 microns, a wall thickness of 200 microns (I.D. = 0.6 mm, O.D. = 1 mm). The hollow-fibers were used to fabricate small laboratory scale modules, containing from 4 to 100fibersabout 10 cm long. For thetestswith real groundwater discussed in the following, large size (2,600 fibers each 45.5 cm long) commercial Enka modules were used. The technique used to impregnate the supports with the carrier solution in n-dodecane has been described in refs. (5) and (6). All hollow-fiber modules were operated in recirculating mode, with feed and strip solutions flowed through the lumen and the shell side of the fibers, respectively, by calibrated peristaltic pumps. Other experimental details concerning the hydrodynamic conditions used in the flat-sheet and hollow-fiber experiments can be found in (5-8), Uranium(IV) Removal from Synthetic Groundwater The challenge of uranium(VI) removal from groundwater consists in finding a compromise between the two somewhat contradictory requirements of high selectivity for U(VI) over Ca(II) and Mg(H) and minimum adjustment of the feed composition. The latter requirement means that neutral and basic extradants (for example, mono- or bi-functional organophosphorus compounds and tertiary amines), showing a high affinity for U(VI), cannot be used as carriers, because they require high concentrations of anions such as nitrate for an effective uranium extraction. Organophosphorous acids, on the other hand, would extract from groundwater at neutral pH not only U(VI) but at least some significant amounts of all other cations with very little selectivity. A compromise solution, suggested by us in (5), was to add sulfuric acid to the groundwater lowering the pH to about 2, where very little Ca and Mg extraction takes place with organophosphorus acids. We thought that this low pH value would not only provide die required selectivity for U(VI) removal, but would also provide the hydrogen ions needed for the subsequent removal of the anionic contaminants in the form of acids by means of a basic carrier in a second membrane module. Of course, at the end of the process, die groundwater should undergo a neutralization step, before being again pumped under ground. Among some organophosphorous acidstestedas U(VI) carriersfromSGW at pH 2, bis(2,4,4-trimethylpentyl)phosphinic acid (H[DTMPeP]), contained in the commercial extradant Cyanex 272, was selected for its superior ability to reject calcium and magnesium. For example, with a 0.1 M solution of Cyanex 272 in ndodecane, it was determined, from distribution experiments, that the selectivity for U(VI) over Ca(II), measured as the ratio of distribution ratios, was - 10 . The next step was to find a suitable stripping agent capable of removing U(VI) from the SLM at the membrane-strip solution interface. The water soluble strong uranium(VI) complexing agent l-hydroxyethane-l,l-diphosphonic acid, HEDPA, was found to be very effective. TTie distribution ratio of U(VI) between 0.1 M Cyanex 272 in n-dodecane and 0.1 M HEDPA in water was measured to be 6x10^, that is, at least 3 orders of magnitude lower than with a 0.1 M solution of oxalic acid. Note here that the use of sodium carbonate, the traditional stripping agent for U(VI) in many solvent extraction studies, produced very short-lived liquid membranes, and, therefore, cannot be considered for the present application. The 9

2.

CHIARIZIAET AL.

Removal of Inorganic ContaminantsfromGroundwater

detailed description of the equilibria involved in the extraction of U(VI) by Cyanex 272 from SGW, and in its stripping by HEDPA, is reported in (J).

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

Uranium(VI) Permeation Studies. Figure 1 shows some typical results of permeation experiments, where the decrease of U(VI), Ca(II) and Fe(III) concentration in the feed is repented as function of time. The concentration data fall on straight lines described by the equation

where C and Co are the feed concentrations of transported species at time t and zero, respectively, A is the membrane area, V is the volume of the feed solution, and Ρ the permeability coefficient (cm s ). In the experiments of Figure 1, Fe(IH) was also studied because this cation is ubiquitous and therefore its behavior is important even though it is not listed as a constituent in the Hanford site groundwater. Figure 1 shows that when 99% of U(VI) is removed from the SGW, after 2.0 hours, only 0.02% of the calcium follows the uranium. This corresponds to a membrane selectivity for U(VI) over Ca(II) equal to 1.6x10* (ratio of permeability coefficients). The data of Figure 1 were obtained with a membrane area equal to 9.8 cm and a feed volume equal to 13 cm . For a much higher value of the A/V ratio, as usually provided by industrial hollow-fiber modules, the time required for the same level of uranium separation would be correspondingly shorter, but the relative contamination of uranium with calcium and iron, that depends on die selectivity, would be the same. Figure 2 shows how the U(VI) permeability coefficients varies with the con­ centration of the membrane carrier (data obtained withflat-sheetsupports). A striking feature of the data is the almost independence of Pu from the carrier concentration over about three orders of magnitude. A membrane initially containing 0.1 M Cyanex 272 in dodecane will continue to operate satisfactorily even when 99% of the carrier is lost due to solubility or other causes. The consequence of this result on the long-term membrane stability is evident. The continuous line of Figure 2 has been calculated with equation 2 _1

2

3

Pu = DuA + Ao t

(2)

where Du = distributionratioof U(VI) between feed and liquid membrane, A = da/D = thickness of aqueous diffusion layer/aqueous diffusion coefficient, cm-s" , and Δο = do/Do = membrane thickness/membrane diffusion coefficient, cm-s*l. How Equation 2 can be used to calculate the aqueous and organic diffusion coefficients of the U(VI) containing species is discussed in detail in (J). To demonstrate that high concentration factors of U(VI) can be reached in practice with our SLM system, experiments were performed in which a 2 L solution of SGW was circulated in a module as die feed, while the strip solution (0.1 M HEDPA) had a volume of 45 mL. After six hours, uranium had been concentrated by a factor 34 in the strip solution. Much higher concentration factors (at least 10 ) can be achieved, however, by using the same strip solution over and over again. We have demonstrated in (5) that a 0.5 M HEDPA stripping solution, containing 0.2 M U(VI), is still very effective in stripping uraniumfrom0.1 M Cyanex 272 in n-dodecane. a

1

a

3

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

26

ENVIRONMENTAL REMEDIATION

Figure 1. U(VI), Ca(H) and Fe(in) removal from SGW at pH 2. Liquid membrane = 0.1 M Cyanex 272 in n-dodecane; Strip = 0.1 M HEDPA; membrane area (hollow-fibers) = 9.8 cm ; feed volume =13 cm ; feed linear velocity = 8.0 cm s . 2

3

_1

10

τ

Ε

ι I I I llllj

I I I I I ! [1|

1 I I I 11 llj

•ft

10"

1 I [ !iιm

a

10"

- 5 l — t i n mil 10" Ί 0 10 4

3

LJL U m i l 10

2

ι ι υ mil 10"'

ι ι 11 m i 10

u

CYANEX 272, M

Figure 2. Permeability coefficient of U(VI) vs. carrier concentration. Feed = SGW at pH 2. Membrane: Cyanex 272 in n-dodecane onflat-sheetsupport; Strip = 0.1 M HEDPA. (Reproduced with permissionfromref. (3). Copyright 1990 M . Dekker, Inc.)

2. CHIARIZIA E T A L .

Removal of Inorganic Contaminants from Groundwater

Removal of Anionic Contaminants from Synthetic Groundwater After passing through a SLM module, in which the uranium separation has taken place, the pH of the groundwater has not been significantly changed by the UO2* - H exchange with the phosphinic acid. As a consequence, the acidic pH of the groundwater can be exploited to remove nitrate, pertechnetate and chromate anions in the form of acids in a second SLM module, containing as carrier a basic molecule capable of reacting with these acids to form membrane soluble salts. After diffusing through the liquid membrane, these salts can be released at the strip side of the membrane, where an alkaline stripping solution (NaOH) ensures that the free carrier is regenerated Three commercially available long-chain aliphatic amines, Primene JM-T (primary), Amberlite LA-2 (secondary), and trilaurylamine (TLA,tertiary),were tested as membrane carriers for nitrate, pertechnetate and chromate anions. Longchain aliphatic amines, dissolved in an organic diluents, are known to extract acids according to the reaction

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

+

+

n

η H +A " +ηΒ

(BH)nA

aggregates

(3)

where H A is a generic acid in the aqueous solution, Β is the amine, and the bar represents organic phase species. Κ is the equilibrium constants that can be taken as a measure of the affinity of the amine for the acid. Table III summarizes the physico-chemical properties of the three amines investigated, of relevance for the choice of the membrane carrier for our specific application. n

Table III.

Properties of Primene JM-T (I), Amberlite LA-2(II) and TLA (III) Chemical affinity forHNOa Κ ι > κ >Km π

for HTCO4

:

Kni2>Kn>Ki K m £ Κπ > K i

Solubility in water

•

Si>Sn>Sni

Interfacial pressure

•

Πι>Π >Πιπ

forH2Cr04

π

Hie detailed determination of the equilibrium constants and of the interfacial behavior of the three amines shown in Table III are reported in refs. (7-8). From the data of Table ΠΙ it appears that the primary amine would not be a good choice as a carrier because, although a better extractant for HNO3, it is a relatively poor extractant for the other two acids. Also, its higher solubility in water and its greater lowering of the interfacialtension(highertendencyto emulsion formation) are an indication that SLM containingftimeneJM-T would be more unstable. The tertiary amine, on the other hand, showing the lowest solubility in water and the best interfacial behavior, exhibits the lowest affinity for HNO3. It seems, therefore, that the best compromise among the properties listed in Table III is the choice of Amberlite LA-2 as the membrane carrier. Anionic Species Permeation Studies. The dependence of the HNO3 permeability coefficient on the concentration of the three amines in n-dodecane (flatsheet membrane experiments) is reported in Figure 3. It appears from the data that,

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

28

ENVIRONMENTAL REMEDIATION

Figure 3. Permeability coefficient of HNO3 .vs. carrier concentration in ndodecane. Feed = ΙΟ* M HNO3; Membrane «flat-sheetsupport; Strip = 0.1 M NaOH. (Reproduced with permission from ref. (7). Copyright 1991 Elsevier Science Publishers B.V.) 2

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

2.

CHIARIZIA ET AL.

Removal of Inorganic ContaminantsfromGroundwater

with the primary and secondary amine, the same limiting Ρ value is reached. Amberlite LA-2, however, reaches the limiting value at a much lower concentration and, therefore, following the same reasoning as for the Cyanex 272 case in Figure 2, is a better carrier for nitric acid. The behavior of Primene JM-T, which has a higher equilibrium constant for HNO3 extraction (see Table ΙΠ), may be due to its higher solubility in water, or simply may reflect the extreme complexity of the aggregation equilibria in the organic phase. The HNO3 permeability coefficient with TLA as carrier is always much lower than for the other two amines, except for very low carrier concentrations. This may indicate that a local precipitation of the nitrate-TLA salt takes place in the pores of the membrane, reducing the speed of permeation. In the groundwater acidified at pH 2 with sulfuric acid, sulfate and bisulfate anions are present. By using an amine as the carrier in a SLM system, it is important to know what fraction of the total H is transported by the liquid membrane as HNO3, because we are interested in removing nitrates, not sulfates, from the groundwater. For this purpose a number of experiments were performed where a pH electrode and a nitrate electrode were used to follow the decrease of acidity and of nitrates in the acidified SGW used as the feed. A detailed discussion of the results is reported in (7). Here it is important only to mention that the removal of nitrates, with all three amines, followed quite closely the removal of total acid. With 0.6 M Amberlite LA-2 as carrier, for example, when 90% of H+ was removed, about 75% of the removable nitrate ions had left die feed This result allowed us to conclude that H is removed from the SGW mainly as nitric acid and that amine based SLMs are effective in removing nitrates from SGW even in the presence of large quantities of sulfate-bisfulfate anions. Membrane experiments showed that the efficiency of the three amines as carriers for Tc(VII) parallels the sequence of equilibrium constants reported in Table III. That is, secondary andtertiaryamines are better at removing Tc(VII) than primary amines. An unexpected result was found investigating the Cr(VI) removal by the three amines. Contrary to the sequence of Table III, the use of TLA as carrier led to a very low value of the QfVT) permeability coefficient, even lower than with Primene JM-T. This result is probably a further indication of the poor solubility of TLA salts (in this case chromate) in n-dodecane. In conclusion, the permeation behavior of the anionic contaminants under study through SLMs containing either one of the amines investigated confirms that the carrier of choice for the simultaneous removal of nitrates, Tc(VH) and Cr(VI) is the secondary amine Amberlite LA-2. +

+

Tests with Real Groundwater Sometestswith 50 gallons samples of groundwater from a specific monitoring well were performed at Hanford using two 2.2 m internal surface area commercial hollow-fiber modules in series, containing a 0.1 M Cyanex 272 and a 0.1 M Primene JM-T solution in n-dodecane, respectively, as liquid membranes. The stripping solutions were 4 gallons of 0.1 M HEDPA for the first module, and 4 gallons of 0.1 M NaOH for the second one. Other experimental details are reported in (6). The result of a typical test are sumarized in Table IV. The results show that the two modules were very effective in reducing die U(VI) and Tc(VII) concentrations by about three and two orders of magnitude, respectively. The limited success with NO3 is due to the fact that thesetestswere performed before the final choice of the best carrier for nitrates was made. The use of a 0.2 M Amberlite LA-II solution as liquid membrane in the second module would have led to much better results for the removal of nitrates. 2

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

30

ENVIRONMENTAL

REMEDIATION

Table IV. Results of Tests with Real Groundwater Time Second Module First Module (hours) Feed TcCVm(oCi/L) FeedU(Vn(PPb) Feed NCK (tram) 786 0 3,460 38.5 4 257 37 361 8 30 31 139 12 7.3 24.7 51 16 2.1 20.9 18 20 1.4 18.1 9 24 15.3 8 — 36 10.2 4 — 48 5.2 2 — FTowrates: 1.5 gal/min, shell side, feed; 1.0 gaVmin, lumen side, strip. Liquid Membrane Stability To test the ability of our liquid membrane system to continuously operate at high efficiency, stability tests were performed. They are described in detail in ref. (6) for the uranium removal from groundwater and in ref. (8) for the removal of die anionic contaminants. Some results are shown in Figure 4, as uranium permeability vs. time (a constant permeability was the criterion for stability), for two modules that were operated without interruption (except nights and weekends) for very long times. An excellent stability, that is constant uranium permeability, was shown by the module with reservoir (it contained a small reservoir of carrier solution ensuring a continuous reimpregnation of the membrane pores). The stability test with this module was interrupted after six months because of the deterioration of die reservoir seal. However, it worked long enough to demonstrate that a properly designed self-reimpregnating module can operate for a practically unlimited time. The conventional module (without reservoir) was periodically impregnated with die carrier solution, when the initial permeability of uranium had declined by about 50%. The procedure was repeated seventimesover a time span of almost 1.5 years. The results reported in Figure 4 show that periodic impregnations of die hollow-fibers are also a viable technique to have modules operating efficiendy for long times. It is interesting to note that the reimpregnation procedure, described in detail in (6), while not affecting the stability of the membrane, had a postive effect on the module performance, measured by the uranium permeability, which improved substantially and progressively after each of the first three reimpregnations. Different strip solutions were used after the last two reimpregnations. In one case a 1 M (instead, of 0.1 M i HEDPA solution was used to see if a much higher osmotic pressure difference between feed and strip solution would affect the stability, in the other case a different stripping agent, a derivative of HEDPA, was tested. Stability tests were also performed with liquid membranes containing each of the three amines investigated as carrier for anions. In the experiments involving liquid membranes adsorbed on flat-sheet supports having a thickness of only 25 microns, the order of stability tertiary > secondary > primary was measured. This is die reverse order of amine solubility in water and of the interfacial lowering at a water-dodecane interface. Both factors, solubility and interfacialtension,seem to be operative in determining the liquid membrane stability, together with the other usual factors, such as support materials, pore size, osmotic pressure gradient and flow rate, which have been kept constant in this work. An impressively high stability was measured in the experiments with flat-sheet membranes, when TLA was the carrier. We think that the high stability of the TLA-dodecane liquid

Removal of Inorganic Contaminants from Groundwater

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch002

CHIARIZIA ET A L

14h

Ο ζ ε 3

CL

2

0

4

10

< QL Ω

16
P {

v a p

to Condense

(5)

In an idealized stripping-gas case, only the VOCs are in the gas phase and should condense since the solvent is considered nonvolatile compared to the VOCs. For a 100 ppm chloroform concentration in sunflower oil at 20°C, the partial pressure of the chloroform (3.2 χ 10" atm) does not exceed its vapor pressure at -60°C, so chloroform alone will not condense at this temperature, as indicated by the data in Table IV. By stripping the solvent at elevated temperatures, the VOCs partial pressure will increase and it should be possible to recover them in a condenser. 5

Table IV. Vapor Pressures of Chloroform in the Condenser Temperature CQ (atm) 20 2.6 χ 10" 0 8.0 χ 10" -20 2.6 χ 10" -40 6.2 χ 10" -60 2.5 χ W Partial pressure of chloroform in the stripping gas is 3.2 χ 10' atmat20°C. 3

1

2

2

3

4

5

Regeneration of the Solvent, Distillation Case In the usual application of solvent extraction for the recovery of dilute VOCs from water, the solvent is regenerated by conventional distillation. This process is applied

ENVIRONMENTAL REMEDIATION

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch004

58

to aqueous systems which have much higher concentrations of contaminants than the ppb concentrations found in groundwater. The distillation procedure requires collection of vapor-liquid equilibrium (VLE) data for the VOC-solvent system before the distillation system can be designed. Typical vapor-liquid equilibrium curves for these VOC-solvent systems are given in Figure 3. This represents the VLE behavior expected for the natural oils and contaminants planned for use in the MASX/MADS process. The extremely dilute VOC region in Figure 3 is of interest for the MASX/MADS process. As seen from the data, the vapor and liquid compositions converge as the VOC becomes more and more dilute. Thus, as the VOC concentration decreases, producing a high purity VOC product becomes increasingly difficult. Generating a high purity VOC productfroma conventional distillation column would require operation at nearly total reflux and be very energy intensive. This problem has limited conventional solvent extraction to much higher concentrated streams, where the recovered solvent is contaminated enough to be regenerated by conventional distillation, and a highly concentrated impurity product is produced as well. In the ppm or ppb region encountered for the MADS, the solvent vapor partial pressure is much higher than the VOC partial pressure. Because of this, by vaporizing and condensing some of the solvent along with the VOC and residual groundwater extracted by the solvent, it should be possible to recover an enriched solution of the VOC in the solvent. For example, a VOC solution of solvent may produce a condensate which is several orders of magnitude more concentrated then the original groundwater. The remaining solvent will have a substantially lower VOC concentration and can then be recycled to the extraction unit Condensing the VOCsolvent vapor will be much easier since its dew point will be much higher than the required temperature to recover the VOCs direcdyfroman inert strip gas, as discussed previously. Enriching the VOC vapor that is condensed to a greater extent will require additional stages, with each MADS stage smaller than the previous one due to the lower liquid flow rate obtained with each enriching step. Advantages of Membranes. The mass transfer rate for this type of separation process is given by J = K a ( C - C* ) L

(6)

Where K a is the mass transfer coefficient, C* is the VOC concentration in the solvent in equilibrium with the vapor phase, C is the actual solvent VOC concentration, and J is the flux of the VOC. Raising the temperature will cause C* to approach zero. For the dilute VOC in the solvent, small values of C cause the flux to approach zero and separation does not occur. By using membranes with their large area to volume ratio, the mass transfer coefficient can be increased by an order of magnitude or more compared to a conventional packed column (33). This increase in area will enhance flux despite small values of C, thus making the separation more feasible. The VLE data needed to evaluate the MASX/MADS process are currently being collected. It is expected that this process will perform well. L

Conclusions Membrane-assisted solvent extraction of dilute VOCsfromgroundwater is technically feasible. The regeneration of the solvent is the difficult step in the development of the process. It is not feasible to air strip the solvent at ambient conditions due to the low partial pressures of the VOCs above the solvent. These low partial pressures in the strip gas make the VOCs impossible to recover with a condenser. However, by using

4.

Decontamination of Groundwater

HUTTER & VANDEGRIFT

59

250

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch004

Temp. °C

50 J OA

0

,

, 0.2

,

, 0.4

,

, 0.6

,

. 0.8

,

1 1

Mole Fraction VOC Figure 3. Vapor-liquid equilibrium for the VOC-solvent system. a membrane-assisted vaporization procedure, the VOCs can be recovered from the organic phase. Some vaporization of the solvent will occur, and this two-phase system will condense at a dew point much higher than the required temperature to recover the VOCs directlyfroman inert strip gas. Work supported by the U.S. Department of Energy, Separation Science and Technology Program, under Contract W-31-109-Eng-38.

Literature Cited 1

Brown, R. Α., Sullivan, K. Poll. Eng. 1991, 23, 62-68. Moos, L. P., Duffy, T. L. 1990 Annual Site Environmental Report:; ANL-90/8, Argonne National Laboratory, Argonne, IL, 1990. Goodrich, J. Α., Lykins, B. W., Clark, R. M . , Oppelt, Ε. T. J. AWWA March 1991, 55-62. DeWalle, F. P., Chian, E. S. K. J. AWWA April 1981, 206-211. Stuermer, D. H., Ng, D. J., Morris, C. J., Env. Sci. Tech. 1982, 16, 582-587. Reinhard, M., Goodman, N. L., Barker, J. F. Env. Sci. Tech. 1984, 18, 953-961. Roberts, A. J., Thomas, T. C. Env. Tox. Chem. 1986, 5, 3-11. Forst, C., Roth, W., Kuhnmunch, S. Int. J. Env. Anal. Chem. 1989, 37, 287-293. 9U. S. Environmental Protection Agency, Drinking Water Regulations and Health Advisories, April 1990. Sandall, O. C., Shiao, S. Y., Myers, J. E. AIChE Sym. Ser. 1975, 70, 24-30. 11Hwang, S. T. AIChE Sym. Ser. 1981, 77, 304-315. 12Ricker, N. L., King, C. J. AIChE Sym. Ser. 1978, 74, 204-209. Hewes, C. G., Smith, W. H., Davis, R. R. AIChE Sym. Ser. 1975, 70, 54-60. Earhart, J. P., Won, K. W., Wong, Η. Y., Prausnitz, J. M . , King, C. J. CEP May 1977, 67-73. 15Ewell, R. H., Harrison, J. M., Berg, L. Ind. Eng. Chem. 1944, 36, 871-875. 16Joshi, D. K., Senetar, J. J., King, C. J., Ind. Eng. Chem. Proc. Des. Dev. 1984, 23, 748-754. 2

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Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch004

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Barbari, Τ. Α., King, C. J. Env. Sci. Tech. 1982, 16, 624-627. 18King, C. J., Barbari, T. Α., Joshi, D. K., Bell, Ν. E., Senetar, J. J. Equilibrium Distribution Coefficients for Extraction of Chlorinated Organic Priority Pollu from Water-1EPA-600/2-84-060a; U. S. Dept. of Commerce, National Technical Information Service: Springfield, VA, 1984. 19King, C. J., Barbari, Τ. Α., Joshi, D. K., Bell, Ν. E., Senetar, J. J. Equilibrium Distribution Coefficients for Extraction of Chlorinated Organic Priority Pollu from Water -2 EPA-600/2-84-060b; U. S. Dept. of Commerce, National Technical Information Service: Springfield, VA, 1984. 20Hager, D. G., Physical/Chemical Processes Innovative Hazardous Waste Trea Technology Series ; Freeman, H. M., Ed., Innovative Hazardous Waste Treatment Technology Series-Volume 2; Technomic: Lancaster, PA, 1990, 143-154. 21Roulier, M . , Ryan, J., Houthoofd, J., Pahren, H., Custer, F., Physical/Chemical Processes Innovative Hazardous Waste Treatment Technology Series ; Fr H. M., Ed., Innovative Hazardous Waste Treatment Technology Series-Volume 2; Technomic: Lancaster, PA, 1990, 199-204. Prasad, R., Sirkar, Κ. K. AIChE J. 1987, 33, 1057-1066. 23Chemical Engineers Handbook, Perry, R. H., Green, D. W., Eds., McGraw-Hill: Highstown, NJ, 1989, 17-14 - 17-34. Zander, A. K., Qin, R., Semmens, M . J. J. Env. Eng. 1989, 115, 768-784. Prasad, R., Sirkar, Κ. K. Sep. Sci. Eng. 1987, 22, 619-640. Prasad, R., Frank, G. T., Sirkar, Κ. K. AIChE Symp. Ser. 1988, 84, 42-53. Callahan, R. W. AIChE Symp. Ser. 1988, 84, 54-63. 28Rosen, M . J., Surfactants and Intertacial Phenomena, John Wiley & Sons, Inc.: New York, NY, 1978, 174-184. 29Semmens, M . J., Method of Removing Organic Volatile and Semivolatile Contaminants from Water, U. S. Patent # 4960520, 1990. 30Millipore, Analysis, Purification, Monitoring, Quality Control, 1990 Catalog. Leonard, R. Α., Chemical Technology Division Annual Report, 1989, ANL-90/11, Argonne National Laboratory, Argonne, IL, 1990. 32Byers, W. D., Physical/Chemical Processes Innovative Hazardous Waste Treatment Technology Series ; Freeman, H. M., Ed., Innovative Hazardous Waste Treatment Technology Series-Volume 2; Technomic: Lancaster, PA, 1990, 19-29. Zander, A. K., Semmens, M . J., Narbaitz, R. M . J. AWWA 1989, 81, 76-81. 34Chaiko, D., Osseo-Asare, K. Sep. Sci. Tech. 1982, 17, 1659-1667. 22

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1992

Chapter 5

Low-Temperature Transportable Technology for On-Site Remediation 1

Michael G. Cosmos and Roger K. Nielson

2

l

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

2

Roy F. Weston, Inc., West Chester, PA 19380 SoilTech, ATP Systems, Inc., 6300 Syracuse Way, Suite 300, Englewood, CO 80111 An innovative technology, the Low Temperature Thermal Treatment (LT3) System was developed by Roy F. Weston, Inc. to treat soils, sludges and sediments contaminated with volatile and s e m i v o l a t i l e organic compounds. The L T process was utilized to remediate a contaminated s i t e near Crows Landing, CA. The processed soil was t r e a t e d to l e s s than 5 ppm of t o t a l petroleum hydrocarbons. During operation stack emissions were analyzed to determine emission c h a r a c t e r i s t i c s . 3

L a r g e q u a n t i t i e s o f s o i l s l u d g e s and s e d i m e n t s have been c o n t a m i n a t e d w i t h l o w l e v e l s o f o r g a n i c c h e m i c a l s as t h e r e s u l t o f l e a k i n g s t o r a g e t a n k s , w a s t e d i s p o s a l a c t i v i t i e s and i n d u s t r i a l o r c o m m e r c i a l o p e r a t i o n s . The t r e a t m e n t o f l a r g e q u a n t i t i e s o f i m p a c t e d s o i l s i s e x p e n s i v e when u s i n g e x i s t i n g t h e r m a l t e c h n o l o g i e s such as i n c i n e r a t i o n . To p r o v i d e a n e f f e c t i v e and c o s t e f f i c i e n t method o f t r e a t i n g o r g a n i c c o n t a m i n a t e d s o i l s Roy F . W e s t o n , I n c . h a s d e v e l o p e d and p a t e n t e d i t s Low T e m p e r a t u r e T h e r m a l T r e a t m e n t (LT ) System (U.S. Patent No. 4 , 7 3 8 , 2 0 6 ) . 3

LT

3

Process D e s c r i p t i o n 3

The b a s i s o f t h e L T t e c h n o l o g y i s t h e thermal p r o c e s s o r , w h i c h i s an i n d i r e c t h e a t e x c h a n g e r u s e d t o d r y and h e a t c o n t a m i n a t e d s o i l s . H e a t i n g t h e s o i l s t o a p p r o x i m a t e l y 500°F i n t h e p r o c e s s o r e v a p o r a t e s o r s t r i p s t h e o r g a n i c s from t h e s o i l . The o r g a n i c v a p o r s a r e t h e n v e n t e d t h r o u g h two c o n d e n s e r s w h i c h o p e r a t e 0097-6156/92/0509-0061$06.00/0 © 1992 American Chemical Society

62

ENVIRONMENTAL REMEDIATION

i n s e r i e s t o condense and remove organic compounds. The vapor stream i s subsequently t r e a t e d by carbon adsorption. Treated gases are discharged t o the atmosphere. The condensate stream, which i s p r i m a r i l y the inherent s o i l moisture, i s a l s o t r e a t e d by carbon adsorption. Treated water i s reused as c o o l i n g water i n the s o i l c o n d i t i o n e r or as dust c o n t r o l i n excavation and b a c k f i l l areas. Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

3

The LT system i s d i v i d e d i n t o three main areas of emphasis: s o i l treatment, emissions c o n t r o l , and water treatment. A schematic diagram of the LT process i s shown i n Figure 1. The LT process equipment i s mounted on three t r a c t o r t r a i l e r beds f o r t r a n s p o r t a t i o n and operation. The u n i t i s s u i t a b l e f o r highway t r a n s p o r t . The general arrangement of the process equipment and the placement of the t r a i l e r s during operation i s shown on Figure 2. 3

3

Soil

Treatment

S o i l Feed System. Excavated s o i l i s transported to the system by a front-end loader. The front-end loader c a r r i e s the s o i l over a weigh s c a l e . The s o i l weight i s recorded f o r each load t r a n s p o r t e d t o the power shredder. S o i l i s deposited d i r e c t l y i n t o the power shredding device. C l a s s i f i e d s o i l with a top s i z e of l e s s than 2 inches passes through the shredder i n t o the feed conveyor. Oversized m a t e r i a l i s removed and s t o c k p i l e d i n a r o l l - o f f container. The feed conveyor discharges i n t o the surge hopper l o c a t e d above the thermal processor. The s o i l w i l l be fed i n t o the LT system at regular i n t e r v a l s t o maintain the surge hopper s e a l . The surge hopper a l s o provides a s e a l over the thermal processor t o minimize a i r infiltration. 3

Thermal Processor. The thermal processor c o n s i s t s of two jacketed screw conveyors. The s h a f t s and f l i g h t s of the screw conveyors and the trough j a c k e t s are hollow t o allow c i r c u l a t i o n of a heat t r a n s f e r f l u i d ( i . e . , hot o i l ) . The f u n c t i o n of each screw conveyor i s t o move s o i l forward through the processor and t o thoroughly mix the m a t e r i a l , p r o v i d i n g i n d i r e c t contact between the heat t r a n s f e r f l u i d and the s o i l . The troughs are assembled i n a piggyback fashion (one above the o t h e r ) . Each trough houses four intermeshed screw conveyors. The screw conveyors are intermeshed t o break up s o i l clumps and t o improve heat t r a n s f e r . The four screws of each processor are driven by a v a r i a b l e speed d r i v e

Feed conveyor

Dust

Surge hopper

3

Feed soil Discharge conveyor

Water tank

Refrigerated condenser

To atmosphere

Carbon adsorption

Vapor

Carbon adsorption

Water

3-Phase oil/water separator

Processor off-gases

ti

Induced draft fan

Air-cooled condenser

Fabric filter

Thermal processor

Hot Cool bil [oil Treated soil

Hot oil system

Makeup water

Spray water

55-Gallon drum

Organics

Conditioner (Conveyor) Truck feed conveyor

To backfill excavation area

Processed soil dump truck

- Fuel/combustion air

i i Hot oil burner off-gases

To atmosphere

Figure 1. Schematic flow diagram of the LT process. (Reproduced with permission from Roy F. Weston, Inc.)

Oversize material

Clay Shredder

Contaminated soil storage

Sweep gas

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

ο ζ

Ώ ft» 25 m ζ

ο

ο ο

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

64

ENVIRONMENTAL REMEDIATION

n u

Equipment A. Thermal Processors B. Fabric Filter C. Process Control Trailer (Office) D. Thermal Processor Drive Units E. Hot Oil System F. Air-cooled Condenser G. Induced Draft Fan H. Refrigerated Condenser I.

Vent Condenser

J.

Glycol/Water Pumps

K. Glycol/Water Reservoir L

Heater

M. Vapor Fan N. Vapor Phase Carbon Columns O. Oil/Water Separator P.

Liquid Phase Carbon Pumps

Q. Organic Collection Drums R.

Liquid Phase Carbon Columns

S.

Clay Shredder

T.

Drag Conveyor

U.

Discharge Conveyor

V.

Dump Truck

Ρ

0 0Ό Γ

­ α

3

Figure 2. General arrangement of LT system. (Reproduced with permission from Roy F. Weston, Inc.)

5.

COSMOS

& NIELSON

Transportable Technology for Οη-Site Remediation

mechanism. Residence time and s o i l temperature i n the thermal processor are adjusted by v a r y i n g the r o t a t i o n a l speed of the screws and the hot o i l temperature s e t t i n g .

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

Vapors are d r i v e n o f f the s o i l and are drawn out of the thermal processor by an induced d r a f t (ID) fan. The d r a f t created by the ID fan i s maintained i n the processor t o allow the vapors t o be removed from the processor. Processed S o i l Handling System. Soil i s discharged from the thermal processor i n t o a h o r i z o n t a l screw conveyor. The h o r i z o n t a l screw conveyor discharges t o a second screw conveyor, or ash c o n d i t i o n e r . The ash c o n d i t i o n e r i s a ribbon f l i g h t screw conveyor. Water spray nozzles are i n s t a l l e d i n the ash c o n d i t i o n e r housing t o c o o l the discharged s o i l and t o minimize f u g i t i v e dust emissions. The c o n d i t i o n e r discharges onto an i n c l i n e d stacker b e l t . The stacker b e l t conveys the wetted processed s o i l from the c o n d i t i o n e r t o a dump truck. Hot O i l System. The hot o i l system i s a s e l f contained u n i t c o n s i s t i n g of a 7.2 m i l l i o n B r i t i s h thermal u n i t s per hour (Btu/hr) g a s - f i r e d burner, flame supervisory system, o i l r e s e r v o i r , hot o i l pump and a s s o c i a t e d c o n t r o l s . The hot o i l system burner provides the thermal energy t o maintain the temperature of the heat t r a n s f e r o i l used t o i n d i r e c t l y v o l a t i l i z e organics from the s o i l . A p o r t i o n of the combustion gases r e l e a s e d from the hot o i l system i s used as sweep gas i n the thermal processor. The warm sweep gas ( i . e . , 700°F and very low oxygen content) removes the organics from the processor. Sweep gas i s introduced t o maintain an exhaust gas temperature from the processor of about 350°F. The sweep gas a l s o provides an inert atmosphere t o avoid exceeding the lower explosive limit (LEL) of contaminants w i t h i n the thermal processor and downstream equipment. The remaining p o r t i o n of combustion gases from the o i l system i s released f o r atmospheric discharge. Emission Control System. An emission c o n t r o l system i s provided t o prevent the r e l e a s e of p a r t i c u l a t e matter or organic vapors. The c o n t r o l devices are described i n t h i s subsection and include the f a b r i c

6

66

ENVIRONMENTAL REMEDIATION

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

f i l t e r , a i r - c o o l e d condenser, induced d r a f t (ID) fan, r e f r i g e r a t e d condenser, and a c t i v a t e d carbon system. F a b r i c F i l t e r . Sweep a i r and organics from the thermal processor are drawn by the ID fan i n t o a f a b r i c f i l t e r f o r p a r t i c u l a t e (dust) removal. The f a b r i c f i l t e r i s of the j e t - p u l s e design, where a i r at a pressure of 80 pounds per square inch gauge (psig) periodically pulses t o remove dust that has accumulated on the bags. Dust drops t o the bottom of the f a b r i c f i l t e r and i s c o l l e c t e d i n two c o l l e c t i o n bins. Dust i s manually removed from the f a b r i c filter. M r - C o o l e d Condenser. The exhaust gas from the f a b r i c f i l t e r i s drawn i n t o an a i r - c o o l e d condenser by the ID fan. The a i r - c o o l e d condenser i s used t o remove condensible water vapor and organics from the exhaust gas. Condensed l i q u i d i s c o l l e c t e d i n a t r a p and i s pumped t o the water treatment system. Condenser off-gases are d i r e c t e d t o the second ( r e f r i g e r a t e d ) condenser. R e f r i g e r a t e d Condenser. The f u n c t i o n of the r e f r i g e r a t e d condenser i s t o f u r t h e r lower the temperature and moisture content of the exhaust gases, thereby reducing the water/organic load on the vapor phase carbon system. Saturated exhaust gas from the a i r - c o o l e d condenser enters the refrigerated condenser at 125°F. C i r c u l a t i n g glycol/water s o l u t i o n i n d i r e c t l y cools the process gas t o 60°F. The glycol/water s o l u t i o n i s continuously r e c y c l e d through a r e f r i g e r a t o r that maintains the glycol/water temperature. The process gas i s then reheated t o 70°F by three e l e c t r i c r e s i s t a n c e heaters. The r e l a t i v e humidity of the exiting gas is 70%, preventing further condensation i n the process p i p i n g , and optimizing the a c t i v a t e d carbon adsorption e f f i c i e n c y . Induced Draft (ID) Fan. The ID fan i s used t o induce a i r flow through the thermal treatment system and prevent f u g i t i v e emissions of dust on v o l a t i l e organics. Vapor-Phase Carbon Adsorption System. The f u n c t i o n of the vapor-phase a c t i v a t e d carbon columns i s t o remove the remaining organics from the exhaust fumes e x i t i n g the r e f r i g e r a t e d condenser.

5.

COSMOS & NIELSON

Transportable Technology for On-Site Remediation

A p p r o x i m a t e l y 99% o f t h e o r g a n i c s e n t e r i n g t h e c a r b o n u n i t w i l l be removed from t h e v a p o r s t r e a m .

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

The s y s t e m i n c l u d e s two c a r b o n c o l u m n s . The v a p o r phase carbon columns a r e o p e r a t e d i n p a r a l l e l t o a l l o w i s o l a t i o n and a c c e s s t o one c o l u m n w h i l e t h e o t h e r i s on-line. The g a s e s e x i t i n g t h e c a r b o n c o l u m n s may c o n t a i n t o t a l o r g a n i c c o n c e n t r a t i o n s up t o 4 p a r t s p e r m i l l i o n (ppm) by v o l u m e . The exhaust gas from the carbon columns is c o n t i n u o u s l y m o n i t o r e d f o r t o t a l h y d r o c a r b o n (THC) concentrations. I f t h e THC c o n c e n t r a t i o n e x c e e d s 10 ppm, t h e c a r b o n w i l l be c o n s i d e r e d " s p e n t " and an a l a r m w i l l be a c t i v a t e d . C o n t i n u o u s E m i s s i o n s M o n i t o r i n g (CEM) S y s t e m . An e x t r a c t i v e - t y p e c o n t i n u o u s e m i s s i o n s m o n i t o r i n g (CEM) system i s used t o monitor the carbon column exhaust g a s e s f o r o x y g e n , c a r b o n d i o x i d e , c a r b o n monoxide and t o t a l h y d r o c a r b o n s . The CEM s y s t e m a l s o m o n i t o r s t h e e x h a u s t g a s e s from t h e f a b r i c f i l t e r (air-cooled c o n d e n s e r i n l e t ) f o r o x y g e n and t o t a l h y d r o c a r b o n s . C o n d e n s a t e H a n d l i n g S y s t e m . The c o n d e n s a t e from t h e L T s y s t e m i s s e p a r a t e d i n t o l i g h t and h e a v y o r g a n i c compounds and w a t e r . The aqueous p h a s e (water) is t r e a t e d by c a r b o n a d s o r p t i o n and r e c y c l e d t o t h e L T process. The o r g a n i c p h a s e s a r e d i s p o s e d o f a t an o f f - s i t e permitted f a c i l i t y . The c o n d e n s a t e h a n d l i n g system i s d e s c r i b e d i n t h i s s u b s e c t i o n . 3

3

Oil-Water Separator. L i q u i d e x i t i n g both the a i r - c o o l e d and r e f r i g e r a t e d c o n d e n s e r s i s c o l l e c t e d and pumped t o a 3 - p h a s e o i l - w a t e r s e p a r a t o r a l l o w i n g t h e i n s o l u b l e l i g h t and h e a v y o r g a n i c components t o s e p a r a t e from t h e w a t e r . The l i g h t o r g a n i c p h a s e i s removed b y a skimmer and w e i r . The h e a v y o r g a n i c p h a s e i s removed t h r o u g h a d r a i n . The w a t e r p h a s e f l o w s o u t o f t h e s e p a r a t o r and i s d i r e c t e d t o t h e l i q u i d - p h a s e carbon adsorption system. C a r b o n A d s o r p t i o n . The w a t e r removed from t h e o i l - w a t e r s e p a r a t o r i s d i r e c t e d t h r o u g h two c a r b o n a d s o r p t i o n columns t h a t o p e r a t e i n s e r i e s f o r removal of s o l u b l e o r g a n i c s . The l i q u i d s t r e a m between t h e two c a r b o n c o l u m n s i s r o u t i n e l y s a m p l e d t o d e t e c t breakthrough i n the f i r s t carbon column.

68

ENVIRONMENTAL REMEDIATION

3

Utilities. Operating the LT system requires the f o l l o w i n g support systems and u t i l i t i e s : E l e c t r i c a l power Diesel fuel Natural gas Process water

•

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

Case Study 3

The LT system was a p p l i e d a t a s i t e near Crows Landing, CA t o remediate 1,400 tons of s o i l . The s o i l was contaminated with f u e l o i l , j e t f u e l , and spent s o l v e n t s . The s o i l was contaminated as the r e s u l t of f u e l and solvents s p i l l e d i n the f i r e t r a i n i n g p r a c t i c e area. The s o i l was impacted with BTEX, (Benzene, toluene, e t h y l benzene and xylene) as w e l l as total petroleum hydrocarbons. Site c h a r a c t e r i z a t i o n data c o l l e c t e d i n 1988 i n d i c a t e d concentrations of TPH up t o a maximum of 5,400 ppm. The c h a r a c t e r i z a t i o n data was compiled from surface samples and s o i l borings i n the impacted area. The average composition of the t e n samples i n the impacted area was 619 ppm. During processing, grab samples were c o l l e c t e d from the untreated m a t e r i a l as i t was fed t o the processor. The concentrations were nonuniform and range from 97 ppm t o non detected (1 ppm d e t e c t i o n l i m i t ) . The average concentration of the grab samples was 52 ppm ± 3 2 ppm. 3

The LT system was mobilized t o the s i t e a f t e r preparation of a d e t a i l e d s i t e s p e c i f i c Work Plan and Health and Safety Plan. An A i r Permit was received from the S t a n i s l a u s County A i r Resources Board. The s o i l was excavated from a 50 f t . by 50 f t . area. During treatment the t r e a t e d s o i l was composited d a i l y and analyzed using a Hanby Environmental Test K i t f o r petroleum hydrocarbons. T h i s simple t e s t k i t , which provides r a p i d s o i l a n a l y s i s , was used as a means of process c o n t r o l . The processed s o i l operating temperature and r e t e n t i o n time was optimized at 422°F and 22 minutes, r e s p e c t i v e l y . The t r e a t e d s o i l samples were c o l l e c t e d and analyzed f o r TPH and BTEX s by an independent t h i r d party. The average of the 18 samples collected and analyzed using approved a n a l y t i c a l techniques are provided on Table I. The t r e a t e d s o i l exceeded the treatment c r i t e r i a of 100 ppm t o t a l petroleum hydrocarbons and 700 ppb toluene. 1

5.

COSMOS & NIELSON

Transportable Technology for On-Site Remediation

Table I . Average Treated S o i l Results T o t a l Petroleum Hydrocarbons Benzene

b

Toluene

6

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch005

5.2 ± 8


39

(40)

LLC

2L1

•f Measured By Various Techniques

(24)

70

0.89

Ebul.

Las*

6.51

GC

3

60

50

25

Temp°C

Table Π. γ°° For Solutes in Water Measured by Several Researchers Using Various Techniques

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch016

1-Butanol

2-Butanone

Isopropanol (continued)

Solute in Water

20

(24)

(21)

90

55.5

(23)

21

23

46.5 57.2< >

21

80

59.3

60

20

14.00< >

59.3< > 67.8< >

u

20

13.68< >

70

49.5< >

5

14

50.5< > 51.6" >

40

25

20

30

25

100

90

11.6^

U

85

(15)

3

13.62< >

278

GC

9

2

4 . (29)

.4

41

29

26)

26< 25.6< >

35

45.1< >

37

29.5< >

40

(39)

206< >

72

39

41.2^ 66< >

Table II. Continued. γ~ Measured By Various Techniques LLC GS HS Ebul.

80

76

Temp°C

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch016

52

13.1

1

41

(sol)"

I I ο Ο as

ο % m

Published on October 27, 1992 on http://pubs.acs.org | doi: 10.1021/bk-1992-0509.ch016

16.

Limiting Activity Coefficients ofNonelectmlytes

BERGMANN & ECKERT

ο

ο

CM

oo