Municipal Solid Waste Incinerator Residues [1 ed.] 0444825630, 9780444825636

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MUNICIPAL SOLIDWASTE INCINERATORRESIDUES

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Studies in Environmental Science 67

MUNICIPAL SOLID WASTE INCINERATOR RESIDUES The INTERNATIONAL c o m p r i s e d of

ASH WORKING GROUP,

(in alphabetical order):

A. John Chandler

David S. Kosson

A.J. Chandlerand Associates Ltd., Willowdale, Ontario, Canada

Rutgers, The State University of New Jersey, New Brunswick, New Jersey U.S.A.

T. Taylor Eighmy

Steven E. Sawell

University of New Hampshire, Ourham, New Hampshire, U.S.A.

Compass Environmental, Burlington, Ontario, Canada

Jan Hartl6n

Hans A. van der Sleet

Swedisch GeotechnicalInstitute, LinkEping, Sweden

Netherlands EnergyResearchFoundation, Petten, The Netherlands

Ole Hjelmar

JiJrgen Vehlow

VKI WaterQuality Institute, Hersholm, Denmark

Forschungszentrum Karlsruhe GmbH, Institute of TechnicalChemistry, Karlsruhe, Germany

1997 ELSEVIER Amsterdam

-

Lausanne

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NewYork-

Oxford -

Shannon

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Tokyo

ELSEVIER SCIENCE B.V. Sara Burgerhartstraat 25 P.O. Box 211, 1000 AE Amsterdam, The Netherlands

ISBN 0-444-82563-0 © 1997 ELSEVIER SCIENCE B.V. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science B.V., Copyright & Permissions Department, P.O. Box 521, 1000 AM Amsterdam, The Netherlands. Special regulations for readers in the U.S.A. - This publication has been registered with the Copyright Clearance Center Inc. (CCC), 222 Rosewood Drive Danvers, Ma 01923. Information can be obtained from the CCC about conditions under which photocopies of parts of this publication may be made in the U.S.A. All other copyright questions, including photocopying outside of the U.S.A., should be referred to the publisher. No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. This book is printed on acid-free paper. Printed in The Netherlands

PREFACE

The International Ash Working Group (IAWG) was established in 1989 to conduct an in-depth review of the existing scientific data and develop a state-of-knowledge treatise on MSW incinerator residue characterisation, disposal, treatment and utilisation. The topics of operator and worker health and safety, and health risk assessment were beyond the scope of this project, and therefore have not been addressed. Members of the IAWG had been involved in various research and development programs concerning MSW incineration residues for several years prior to establishing the IAWG. The IAWG has met regularly since its inception to discuss aspects of residue characterisation and management, as well as offering a forum for other researchers to provide their perspectives on the issues. The project soon grew beyond the original scope, due in part to the need to examine the ever increasing volume of published research data which became available in the early 1990's. In addition, the IAWG project was designated as an Activity under the International Energy Agency's (lEA) Bioenergy Agreement Task Xl - Conversion of MSW to Energy 1991 - 1994. This final treatise and the Summary Report represent the culmination of the IAWG efforts over the period from February 1990 through July 1996. The input of information from colleagues, along with other information available from the literature and personal contacts, was used to formulate the conclusions and recommendations summarised in this document. The results of this effort have been presented in extended seminars, in conjunction with both the WASCON '94 Conference (June 1994) in Europe and with the Municipal Waste Combustion Conference (April 1995) in North America. In addition, the IAWG co-sponsored and participated in the "Seminar on Cycle and Stabilisation Technologies of MSW Incineration Residues" along with the Japan Waste Research Foundation (March 1996) in Japan. Currently, the IAWG continues to operate as a sub-group of Thermal Conversion Activity under the IEA's Bioenergy Agreement Task XlV - Energy Recovery from Municipal Solid Waste.

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AUTHORS A. John Chandler A. J. Chandler and Associates, Ltd. Willowdale, Ontario Canada T. Taylor Eighrny University of New Hampshire Durham, New Hampshire United States of America Jan Hartldn Swedish Geotechnical Institute Linkoping Sweden Ole Hjelmar Danish Water Quality Institute H~rsholm Denmark David S. Kosson Rutgers, The State University of New Jersey New Brunswick, New Jersey United States of America Steven E. Sawell Compass Environmental Burlington, Ontario Canada Hans van der Sloot Netherlands Energy Research Foundation Petten The Netherlands Jtirgen Vehlow Forschungszentrum Karlsruhe GmbH Institute of Technical Chemistry Germany

... VIII

THE INTERNATIONAL ASH WORKING GROUP

A. John Chandler A. J. Chandler and Associates, Ltd. Willowdale, Ontario Canada

Shin-ichi Saki (Since 1994) Environment Preservation Centre Kyoto University Japan

T. Taylor Eighmy University of New Hampshire Durham, New Hampshire United States of America

Steven E. Sawell Compass Environmental Burlington, Ontario Canada

Jan Hartl6n Swedish Geotechnical Institute Linkoping Sweden

Hans van der Sloot Netherlands Energy Research Foundation Petten The Netherlands

Ole Hjelmar Danish Water Quality Institute H~rsholm Denmark David S. Kosson Rutgers, The State University of New Jersey New Brunswick, New Jersey United States of America

JQrgen Vehlow Forschungszentrum Karlsruhe GmbH Institute of Technical Chemistry Germany

DISCLAIMER This report was prepared by the International Ash Working Group (IAWG). The work was sponsored by the agencies listed herein, who are not necessarily in agreement with the opinions expressed by the IAWG. Neither the sponsoring agencies (including its members), nor the IAWG, nor any other person acting on their behalf makes any warranty, express or implied, or assumes any legal responsibility for the accuracy of any information or for the completeness or usefulness of any apparatus, product or process disclosed, or accept liability for the use, or damages resulting from the use, thereof. Neither do they represent that their use would not infringe upon privately owned rights. The IAWG also does not, and never intended to, discuss or make recommendations with regard to health and safety issues concerning facility operators or workers. Furthermore, the sponsoring agencies and the IAWG hereby disclaim ANY AND ALL WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, WHETHER ARISING BY LAW, CUSTOM, OR CONDUCT WITH RESPECT TO ANY OF THE INFORMATION CONTAINED IN THIS REPORT. In no event shall the sponsoring agencies or the IAWG be liable for incidental or consequential damages because of the use of any information contained in this report. Any reference in this report to any specific commercial product, process or service by tradename, trademark, manufacturer or otherwise does not necessarily constitute or imply its endorsement or recommendation by the IAWG and the sponsoring agencies or any of its members.

SPONSORING AGENCIES The IAWG is grateful for the financial and technical contributions made to this project by the following agencies/organisations/companies:

Major Sponsors Asea Brown Boveri (Switzerland) Danish Ministry of Energy Energy, Mines and Resources Canada Environment Canada European Commission Forschungszentrum Karlsruhe (Germany) International Energy Agency International Lead Zinc Research Organization Integrated Waste Services Association (USA) Japan Waste Research Foundation LAB (France) Management Office for Energy and the Environment (Netherlands) National Institute of Public Health and Environmental Protection (Netherlands) Swedish National Board for Industrial & Technical Development Takuma Co., Ltd. (Japan) United Kingdom Department of Environment United States Environmental Protection Agency Wheelabrator Environmental Systems (USA)

Minor Sponsors American Society of Mechanical Engineers Greater Vancouver Regional District (Canada) Kubota Corporation (Japan) Northeast Waste Management Officials Association (USA) New Jersey Department of Environmental Protection (USA) Waste Processing Association (Netherlands (WAV))

TECHNICAL CONTRIBUTORS The IAWG gratefully acknowledges the technical contributions made during the course of this project by: T. Aalbers - RIVM, Netherlands M. Adams - VROM, Netherlands I. H. Anthonissen - RIVM, Netherlands J. A t w a t e r - University of British Columbia,Canada J. Barniske - Umweltbundesamt, Germany J. B e r r y - Wheelabrator Environmental Systems Ltd., USA S. B i n n e r - V~lund, Denmark R. B o e h m - PBI, Netherlands H. Borrmann - Forschungszentrum Karlsruhe, Germany J. P. B o r n - VVAV, Netherlands R. Braam - PBI, Netherlands S. Burnley - Energy Technology Support Unit, United Kingdom D. C h a m b a z - BUWAL, Switzerland A. Chamberland - Tiru Inc. (formerly with Montenay Inc.), Canada W. Chesner- Chesner Engineering, P.C., USA B. Christensen - Environment Canada S. C o o k - Bermuda Biological Station R. C o m a n s - ECN, Netherlands S. Dalager- dk TEKNIK, Denmark A. Damborg - Danish Water Quality Institute C. Dent - AEA Technology, United Kingdom A. M. F~llman - Swedish Geotechnical Institute A. Finkelstein - Environment Canada J. Fraser - Wastewater Technology Centre, Canada M. G a l l o - Rutgers University, USA D. Goetz - University of Hamburg, Germany J. G r o n o w - United Kingdom Department of Environment T. Guest - Montenay Inc., Canada L. Gullbrand - Swedish National Board for Industrial and Technical Development G. Hansen - United States Environmental Protection Agency D. Hay - Environment Canada S. Hetherington - Compass Environmental Inc., Canada F. Hoffman - Rutgers University, USA G. Hoffmann - Umweltbundesamt, Germany R. H u i t r i c - LA County Dept. of Sanitation, USA L. Johansson - Swedish Geotechnical Institute B. J o h n k e - Umweltbundesamt, Germany T. Kimura - Kubota Corporation, Japan J. Kiser- Integrated Waste Services Association, USA R. Klicius - Environment Canada O. Knizik - Greater Vancouver Regional District, Canada M. K n o c h e - LAB, France K. Knox - Knox Associates, United Kingdom

T. Kosson - Rutgers University, USA H. K r u i j d e n b e r g - NOVEM, Netherlands P. Leenders- (formerly with VEABRIN - Netherlands) G. Luer s - Corning Glass Ltd., USA T. Lundgren - Terratema AB, Sweden D. Mitchell - AEA Technology (formerly with Warren Spring Laboratory), United Kingdom K. Oberg- Swedish Environmental Protection Agency G. Owen - Environment Canada J. Pappain - Peel Resource Recovery Inc., Canada J. Pearson - AEA Technology, United Kingdom A. Petsonk- Swedish Environmental Protection Agency B. Putnam - International Lead Zinc Research Organization G. Rigo - Rigo & Rigo Associates, Inc., USA J. Robert- Energy, Mines & Resources, Canada F. Roethel - University of New York at Stoney Brook, USA H. Roffman - AWD Technologies, USA S. Sakai - Kyoto University, Japan M. Sheil - New Jersey Dept. of Environmental Protection & Energy, USA B. Simmons - California Board of Health, USA D. St~mpfli - formerly with EAWAG, Switzerland J. Stegemann - Wastewater Technology Centre, Canada L. Stieglitz - Forschungszentrum Karlsruhe, Germany M. Stringer - Greater Vancouver Regional District, Canada H. T e j i m a - Takuma Co., Ltd., Japan T. Theis - Clarkson University, USA B. T i m m - Swedish Environmental Protection Agency J. Tsuji - formerly with Environmental Toxicology International Inc., USA A. van Santen - Energy Technology Support Unit, United Kingdom J. F. Vicard - LAB, France J. Vogel - Heidelberger Zement, Germany H. V o g g - Forschungszentrum Karlsruhe, Germany S. Waring - AEA Technology, United Kingdom C. Wiles - National Renewable Energy Laboratory, USA M. Winka - New Jersey Dept. of Environmental Protection & Energy, USA J. W i t t w e r - Environment Canada D. Wexell -Corning, Inc., USA W. Wormgoor - TNO, Netherlands The IAWG also wishes to thank all of the other people not mentioned here, who in their own way assisted us in this endeavour. A special "thank you" to S t e p h e n H e t h e r i n g t o n for his patient efforts in revising and reformatting this document.

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TABLE OF CONTENTS PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V

CHAPTER 1 - INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 A BRIEF H I S T O R I C A L E X C U R S U S ........................... 1.2 THE D E V E L O P M E N T OF W A S T E I N C I N E R A T I O N ................ 1.3 O B J E C T I V E OF THIS TREATISE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES ...............................................

1 1 2 12 13

CHAPTER 2 - MUNICIPAL SOLID WASTE 2.0 INTRODUCTION ......................................... 2.1 DEFINITION OF M U N I C I P A L SOLID W A S T E . . . . . . . . . . . . . . . . . . . . 2.2 C O M P O S I T I O N OF M U N I C I P A L SOLID W A S T E . . . . . . . . . . . . . . . . . . 2.3 QUANTITY AND MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Denmark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3 France . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.5 Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.6 The Netherlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.7 Sweden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.8 Switzerland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.9 United Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.10 United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 CHEMICAL CONSTITUENTS ................................ REFERENCES ...............................................

15 15 17 21 22 25 26 28 31 32 35 37 37 39 41 51

CHAPTER 3 - MUNICIPAL SOLID WASTE INCINERATION TECHNOLOGIES . . . . . . . . . 3.1 FUEL RECEIPT A N D H A N D L I N G 59 3.2 AVAILABLE COMBUSTION ALTERNATIVES .................... 3.2.1 Mass Burning Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . European Type Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Furnace Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operating Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modular Incineration Systems . . . . . . . . . . . . . . . . . . . . . . . . Other Mass Burn Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Refuse Derived Fuel Systems . . . . . . . . . . . . . . . . . . . . . . . . Semi-Suspension Burning Systems . . . . . . . . . . . . . . . . . . . . Stoker Fired Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59 61 62 62 65 70 73 76 77 79 82 85

xiv Fluidised Bed Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEAT RECOVERY SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IN-PLANT RESIDUE M A N A G E M E N T . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Bottom Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Grate Siftings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Heat Transfer System Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 3.4

85 87 89 90 92 94 95

CHAPTER 4 - AIR EMISSION CONTROL STRATEGIES . . . . . . . . . . . . . . . . . . . . . . 4.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 COMBUSTION CONTROL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compensation for Fuel Variability . . . . . . . . . . . . . . . . . . . . . . Factors Controlling the Chemical Reaction Rate . . . . . . . . . . . 4.2 POST-COMBUSTION C O N T R O L . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Unit Processes For Air Pollution Control . . . . . . . . . . . . . . . . Particulate Matter Control Systems . . . . . . . . . . . . . . . . . . . . Electrostatic Precipitators . . . . . . . . . . . . . . . . . . . . . . . . . . . Fabric Filter (Baghouses) . . . . . . . . . . . . . . . . . . . . . . . . . . . Gaseous Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wet Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dry Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metals Control in Dry Systems . . . . . . . . . . . . . . . . . . . . . . . Mercury Control with Activated Carbon . . . . . . . . . . . . . . . . . NOx Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 TYPICAL APC INSTALLATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Hogdalen, Sweden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Munich South, Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3 Warren County, New Jersey, USA . . . . . . . . . . . . . . . . . . . . 4.3.4 Zirndorf, Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.5 Vestforbr~nding, Copenhagen . . . . . . . . . . . . . . . . . . . . . . . 4.3.6 Lausanne, Switzerland . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.7 Bremerhaven, Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.8 Stuttgart, Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

97 97 97 97 98 98 101 103 103 104 106 109 109 111 112 113 115 118 118 118 122 122 125 125 128 128 131

CHAPTER 5 - REGULATION OF MSW INCINERATORS . . . . . . . . . . . . . . . . . . . . . 5.1 EXISTING MSW INCINERATOR OPERATING GUIDELINES . . . . . . . . 5.1.1 Furnace Temperature and Residence Time . . . . . . . . . . . . . . 5.1.2 Combustion Efficiency and Carbon Monoxide . . . . . . . . . . . . 5.1.3 APC Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Other Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 AIR EMISSION STANDARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Chronological Changes in Emission Standards . . . . . . . . . . . 5.2.2 Emissions of Combustion Products and Acid Gases . . . . . . .

135 137 137 139 139 140 140 141 144

XV

H y d r o g e n Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Particulate Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S u l p h u r Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O x i d e s of Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon M o n o x i d e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Total H y d r o c a r b o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H y d r o g e n Fluoride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trace Metals Emission S t a n d a r d s . . . . . . . . . . . . . . . . . . . . 5.2.3 5.2.4 Trace O r g a n i c Emission S t a n d a r d s . . . . . . . . . . . . . . . . . . . . 5.3 CURRENT ASH AND RESIDUE DISPOSAL PRACTICES .......... 5.3.1 Disposal of Bottom Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . Canada ....................................... Denmark ...................................... France . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G e r m a n y and Switzerland . . . . . . . . . . . . . . . . . . . . . . . . . . Netherlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sweden ....................................... United K i n g d o m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Disposal of Fly Ash and A P C Residues . . . . . . . . . . . . . . . . Canada ....................................... D e n m a r k & the Netherlands . . . . . . . . . . . . . . . . . . . . . . . . . France . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Germany ...................................... Netherlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sweden ....................................... Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3 Utilisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Canada ....................................... Denmark ...................................... France . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Netherlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Germany ...................................... Sweden ....................................... Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES ..............................................

144 144 144 145 145 145 145 145

CHAPTER 6 - ISSUES RELATED TO INCINERATOR ASH SAMPLING . . . . . . . . . . . . 6.0 INTRODUCTION ........................................ 6.1 THE C O N C E P T OF THE REPRESENTATIVE SAMPLE ........... 6.1.1 Waste T y p e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 T y p e of Incinerator/APC S y s t e m . . . . . . . . . . . . . . . . . . . . . 6.1.3 Residue S t r e a m s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 O B J E C T I V E S OF M A T E R I A L S A M P L I N G P R O G R A M S ...........

167 167 167 168 169 170 171

147 149 149 149 149 150 150 150 152 152 152 153 153 153 153 154 154 155 155 155 155 156 156 156 157 157 158 161 161 161

xvi 6.3 6.4

AVAILABLE SAMPLING PROTOCOLS . . . . . . . . . . . . . . . . . . . . . . . . SAMPLING CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Increment Collection Classification . . . . . . . . . . . . . . . . . . . . 6.4.2 Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.3 Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Number of Increments in Composite Sample . . . . . . . . . . . . . 6.4.4 Size of Increments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.5 Collection Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.6 Sampling Streams Other Than Bottom Ash . . . . . . . . . . . . . . Grate Siftings and Heat Recovery Ash . . . . . . . . . . . . . . . . . APC Residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Storage Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sampling from Trucks or Containers . . . . . . . . . . . . . . . . . . . 6.4.7 Sample Preparation Concerns . . . . . . . . . . . . . . . . . . . . . . . Sample Size Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preservation of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laboratory Sample Preparation . . . . . . . . . . . . . . . . . . . . . . Laboratory Sample Subdivision . . . . . . . . . . . . . . . . . . . . . . Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Balance of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAMPLE COLLECTION R E C O M M E N D A T I O N S . . . . . . . . . . . . . . . . . 6.5 6.5.1 Generic Bottom Ash Testing Protocol . . . . . . . . . . . . . . . . . . 6.5.2 Generic Boiler Ash Sampling Protocol . . . . . . . . . . . . . . . . . 6.5.3 Generic APC Residue Sampling Protocol . . . . . . . . . . . . . . . 6.5.4 Documentation of Sampling and Preparation Procedures . . . . E X A M P L E S OF SAMPLING STRATEGIES . . . . . . . . . . . . . . . . . . . . . . 6.6 6.6.1 Bottom Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulatory Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Research Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.2 Grate Siftings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.3 Boiler/Economiser Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulatory Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Research Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.4 Air Pollution Control System Residues . . . . . . . . . . . . . . . . . Regulatory Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Research Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

174 175 175 177 178 178 179 180 181 181 182 182 183 183 183 185 185 186 186 186 187 187 188 188 188 191 192 193 194 194 194 196 197 198 198 199 199 199 200 200

CHAPTER 7 - CHARACTERISATION METHODOLOGIES . . . . . . . . . . . . . . . . . . . . . 7.1 PHYSICAL TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 Visual Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

203 203 203

xvii

7.2

7.3

Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bottom Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fly Ash and APC Residue . . . . . . . . . . . . . . . . . . . . . . . . . . Particle Size Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2 Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dry Sieve Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fine Particle Analyses Methods . . . . . . . . . . . . . . . . . . . . . . 7.1.3 Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bulk Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laboratory Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Field Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.4 Absorption Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Test Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.5 Water Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.6 Proctor Compaction Test . . . . . . . . . . . . . . . . . . . . . . . . . . . Standard Proctor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modified Proctor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.7 Strength and Strength Development . . . . . . . . . . . . . . . . . . . 7.1.8 Bearing Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.9 Durability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Soundness Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LA Abrasion Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Freeze-Thaw Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.10 Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Test Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHEMICAL COMPOSITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size Reduction Techniques . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Inorganic Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Digestion Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specialty Methods for Specific Elements . . . . . . . . . . . . . . . . 7.2.3 Analytical Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . Destructive Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-Destructive Analytical Methods . . . . . . . . . . . . . . . . . . . 7.2.4 Loss on Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.5 Total Carbon, Carbonate, Sulphur and A m m o n i a . . . . . . . . . . 7.2.6 Acid Neutralisation Capacity . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.7 Organic Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHEMICAL SPECIATION M E T H O D S . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Separatory Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . .

203 203 205 205 205 206 206 206 207 207 207 208 208 208 208 209 209 210 210 211 212 212 213 213 214 214 214 221 221 221 223 223 225 226 226 229 232 234 235 236 236 237 237 238 238

xviii Sample Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Particle Size Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . Magnetic Separation Techniques . . . . . . . . . . . . . . . . . . . . . Density Separation Techniques . . . . . . . . . . . . . . . . . . . . . . Selective Phase Dissolution Methods . . . . . . . . . . . . . . . . . . 7.3.2 Impregnation, Thin-Sections, and Thin-Foil Methods . . . . . . . 7.3.3 Analytical Methods for Solid Phase Chemical Speciation . . . . Transmitted Light Microscopy . . . . . . . . . . . . . . . . . . . . . . . Scanning Electron Microscopy ...................... Petrography (Morphology) . . . . . . . . . . . . . . . . . . . . . . . . . . Scanning Tunnelling Microscopy . . . . . . . . . . . . . . . . . . . . . X-Ray Powder Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . Petrography (Mineralogy) . . . . . . . . . . . . . . . . . . . . . . . . . . . Scanning Electron Microscopy/X-Ray Microprobe Analysis . . Scanning-Transmission Electron Microscopy/X-Ray Microprobe Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auger Electron Spectroscopy ....................... X-Ray Fluorescence Spectroscopy . . . . . . . . . . . . . . . . . . . X-Ray Photoelectron Spectroscopy . . . . . . . . . . . . . . . . . . . Secondary Ion Mass Spectroscopy . . . . . . . . . . . . . . . . . . . Electron Energy Loss Spectroscopy . . . . . . . . . . . . . . . . . . . X-Ray Adsorption Spectroscopy and Extended X-Ray Adsorption Fine Structure . . . . . . . . . . . . . . . . . . . . . . . Nuclear Magnetic Resonance . . . . . . . . . . . . . . . . . . . . . . . . Infrared Spectroscopy and Raman Spectroscopy . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

................. MECHANISMS CONTROLLING THE FATE OF ELEMENTS . . . . . . . . 8.1.1 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.2 Processes in the Combustion Chamber . . . . . . . . . . . . . . . . Physical Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sintering and Related Processes . . . . . . . . . . . . . . . . . . . . . Physicochemical Transformations . . . . . . . . . . . . . . . . . . . . . 8.1.3 Mechanisms in the Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . Condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.4 Mechanisms in the Dust Removal System . . . . . . . . . . . . . . 8.1.5 Mechanisms in the Air Pollution Control System . . . . . . . . . . MASS STREAMS IN A MUNICIPAL SOLID WASTE INCINERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LITHOPHILIC ELEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CHAPTER 8 - FATE OF ELEMENTS DURING INCINERATION

8.1

8.2 8.3

240 240 241 242 242 243 245 247 247 247 249 249 250 250 250 251 251 251 252 252 253 253 254 254

263 264 264 265 265 266 272 277 280 280 281 284 285 285 287 287

xix 8.3.2 8.3.3 8.3.4

8.4

Alkali M e t a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Earth-Alkali M e t a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heavy Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromium ...................................... Nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Copper ........................................ VOLATILE ELEMENTS ................................... 8.4.1 Halogens ...................................... Chlorine ...................................... Fluorine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B r o m i n e and Iodine ..............................

288 290 291 292 294 295 295 296 296 297 298 300

Sulphur ....................................... Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Volatile M e t a l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mercury ....................................... Cadmium ...................................... Zinc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arsenic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antimony ...................................... O t h e r Volatile E l e m e n t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 CARBON AND SELECTED CARBON COMPOUNDS ............. 8.5.1 Total C a r b o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.2 P o l y c h l o r i n a t e d D i b e n z o - p - D i o x i n s and -Furans . . . . . . . . . . . 8.5.3 Polychlorinated Biphenyls .......................... 8.5.4 Polychlorinated Benzenes .......................... 8.5.5 Polychlorinated Phenols ........................... 8.5.6 Brominated Hydrocarbons .......................... 8.5.7 Polycyclic A r o m a t i c H y d r o c a r b o n s . . . . . . . . . . . . . . . . . . . . REFERENCES ..............................................

300 302 303 304 305 307 308 310 311 312 312 312 314 320 322 323 324 324 326

CHAPTER 9 - BOTTOM ASH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 PHYSICAL CHARACTERISTICS OF BOTTOM ASH .............. 9.1.1 Gross C o m p o s i t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reject Fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Visual Classification .............................. Water Content .................................. Ferrous C o n t e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Loss on Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D i s s o l v a b l e Solids C o n t e n t . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2 Gravimetric Characteristics ......................... Specific Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Absorption .....................................

339 342 342 342 343 345 346 347 351 351 353 353

XX

Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Percent Fines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.4 Durability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Soundness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abrasion Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5 Geotechnical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . Proctor Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Field Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . California Bearing Ratio (CBR) . . . . . . . . . . . . . . . . . . . . . . . Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.6 Influence of Combustor Type and Operation on Physical 9.1.7 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.8 Influence of Aging on Bottom Ash Physical Characteristics .. PARTICLE MORPHOLOGY, MINERALOGY, AND ALKALINITY OF BOTTOM ASH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.1 Morphology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.2 Mineralogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.3 Alkalinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2.4 Influence of Combustor Type and Operation on Bottom Ash Surface Area, Mineralogy and Alkalinity . . . . . . . . . . . . . . 9.2.5 Influence of Aging on Bottom Ash Surface Area, Mineralogy and Alkalinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INORGANIC CHARACTERISTICS OF BOTTOM ASH . . . . . . . . . . . . . 9.3.1 Elements Present in Bottom Ash . . . . . . . . . . . . . . . . . . . . . 9.3.2 Major Matrix Elements (> 10,000 mg/kg): O,Si,Fe,Ca,AI,Na,K,C . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3 Minor Matrix Elements (1,000 to 10,000 mg/kg): Mg, Ti, CI, Mn, Ba . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.4 Other Minor Elements (1,000 to 10,000 mg/kg): Zn, Cu, Pb, Cr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.5 Other Trace Elements Including Oxyanionic Elements (80%) of the bottom ash produced is utilised in embankment and roadbase applications. Ferrous rejects are recycled.

Sweden It is estimated that Sweden produces 400,000 tonnes of bottom ash and 60,000 tonnes of fly ash and APC residues annually (F~llman and Hartldn, 1992). This quantity fills 250,000 m3 of dedicated monofill space in recently approved disposal sites. Each site has its own permit requirements which were approved by the Environmental Franchise Board. Furthermore, monofills that are used for both bottom ash and APC residues must dispose of these streams in separate cells. Current recommendations suggest that leachate be collected for the initial filling period and after this time infiltration should be kept below 50 mm/year by the use of proper soil covers. The Swedish regulators are currently monitoring disposal requirements developing in the rest of Europe with a view to amending their standards. Regardless of the standards imposed, local citizens are afforded an opportunity to review and comment on any landfill development plans during the approval stages. Efforts to develop a suggested re-use criteria are also under way in Sweden as discussed in the next section. United Kingdom In the United Kingdom, no special provisions exist for the disposal of ash from MSW incinerators, although the issue is under review. All ash generated in society, be it from residential, commercial or industrial establishments, is classified as a "controlled waste". Controlled waste must be disposed at approved licensed facilities that can handle the material. Licensing requirements reflect the need to preserve the environment and ensure neither the water resources nor public health are endangered by the disposal practice. The current practice is to co-dispose with MSW or to use the material as cover in older landfill sites. These sites are under reducing conditions and the theory is that they present a more stable environment for the containment of trace metals. The regulations governing ash disposal are expected to change when the new Air Emissions Regulations force facilities to install new APC systems in 1996. United States Up until the mid 1980s, most MSW incineration residues in the U.S. were disposed in co-disposal situations with MSW. Regulations for disposal varied by state and local situation, and considerable debate and confusion existed about the status of these materials with respect to the RCRA Subtitle C (hazardous waste) testing and management requirements. This was brought about by an exemption for "household waste" from the provisions of Subtitle C. However, in the Spring of 1994, the U.S. Supreme Court ruled that MSW incinerator ash was no longer exempt from testing using the Toxicity Characteristic Leaching Procedure (TCLP). Thus ash (combined or

153 separated bottom ash and APC residues) which passes the criteria associated with the TCLP can be landfilled or monofilled, however, ash which fails the criteria must be disposed as a hazardous waste. This involves disposal in a secure landfill with provisions including a series of liners and leachate collection and treatment facilities which are more stringent than the design criteria for Subtitle C landfills. Most new facilities are using monofills for combined residue disposal, but where space is limited, interest in utilisation is increasing. Although the majority of the facilities combine the residue streams, a small number segregate the bottom and fly ash/APC residue streams to facilitate treatment of the fly ash/APC residue. Furthermore, regulations regarding ash management still vary widely from State to State. For example, New York State requires semi-annual testing for ash and are developing a procedure to handle this material as a special waste (e.g., Bill 10780, State of New York), whereas the State of Florida has permitted the use of ash in artificial marine reef construction projects. Moreover, although some States actively discourage the practice of co-disposal with MSW, other States endorse the practice.

Japan In Japan, the Waste Disposal and Public Cleaning Law, which addresses all aspects of waste disposal, was thoroughly amended in 1991. Under that law, incinerated ash is classified as either bottom ash or fly ash. Bottom ash is treated as normal domestic waste and disposed directly into sanitary landfill sites.

5.3.2 Disposal of Fly Ash and APC Residues The options for handling and disposing of the finer ash streams from incinerators are more limited. Most jurisdictions treat the material as a hazardous waste.

Canada In Canada, the fine ash material must be handled as a hazardous waste. The disposal options include transfer to a hazardous waste disposal facility or treatment of the residues prior to disposal. Various treatment alternatives from disposal in secure landfills to solidification are being evaluated, but there are few regulations in place to evaluate the efficacy of a treatment process. The exception is in British Columbia, where the treated ash must pass a battery of laboratory tests prior to disposal in a conventional landfill. The testing protocol includes evaluating the treated residue using chemical, engineering, durability and leaching tests (Government of British Columbia, 1992).

Denmark & the Netherlands In Denmark, APC residues from the dry or semi-dry processes and fly ash are currently classified as hazardous wastes and are disposed in dedicated monofills with leachate

154 collection systems and bottom liners, and often with impermeable cover layers. Wet scrubber sludges are generally monofilled alone or are mixed with fly ash residues. All of these measures are only considered temporary solutions until suitable treatment systems are made available. At sites in Denmark and the Netherlands, APC residues are stored in polyethylene bags in landfills that have leachate collection systems and bottom liners. Generally, APC residues in the Netherlands are sent to a hazardous waste landfill site, although nearly 40% of the ESP residues from Dutch facilities are currently utilised as a very small percentage filler in asphaltic concrete mixes, but this practice is waning. This residue stream is segregated from all other streams for this purpose.

France The 1991 French law on MSW incineration adopted the EEC directive on air emissions but has tighter mercury and cadmium standards. This has resulted in an increased use of wet APC systems, and hence, more sludge from these systems. The changes in regulations have fostered increased study into ways of modifying residues to meet the disposal criteria mentioned above. Immobilisation of contaminants by solidifying with hydraulic binders is being practised in some areas, and four organisations are currently exploring vitrification alternatives. One manufacturer is utilising the wet scrubber system to modify the residue to meet the criteria (Knoche, 1992).

Germany In Germany, the APC system has to be designed in a way to minimise the production of harmful residues (Bundesministerium, 1993). Heat recovery system ash is separated from dry/semi-dry scrubber residues in some facilities. The fly ash and APC residues are classified as a hazardous waste and requires disposal in either approved landfills or preferably in underground disposal sites such ash old salt mines or in special cells of municipal waste disposal sites. Mehlenweg (1990) estimates that 5% of the total fly ash/APC residue stream (210,000-240,000 tonnes/year)is deposited in underground sites, less than 1% is re-used and the balance goes to surface storage. To minimise the release of dust from surface stored materials, it is packaged in large bags or moistened. German regulations allow boiler/economiser and filter ashes to be modified to reduce the need for controlled disposal, however, few methods have been developed to the commercial scale. Heat recovery and filter ashes along with APC residues contain high quantities of water soluble salts and in Germany they are required to be disposed of in hazardous waste landfills. Limited work has been done to explore the options for treatment/re-use of these materials, but these processes have not progressed beyond pilot scale (Juritsch, 1990; Kurzinger, 1990).

155

Netherlands At the present time, APC residues and fly ash are considered hazardous wastes and are generally managed in a similar manner to that used in Denmark. Sweden In Sweden, APC residues are disposed separately from bottom ash. The Environmental Franchise Board is responsible for setting the requirements for these disposal sites. It has been found that the Swedish infiltration limit of 50ram/year is not suitable for limiting releases from APC residues and fly ash. A new practice is to stabilise these materials before disposal. This is done at one facility in Stockholm by adding 40% low calcium cement to the residue stream. This increases the volume of the stream but further retards the infiltration rate into the material. Other options for the disposal of APC residues and fly ash are currently being examined, including slurry deposition to achieve better compaction, advanced immediate compaction to reduce permeability and the use of plastic covers during deposition to reduce infiltration. Japan In Japan, fly ash and APC residues are treated as a domestic waste under special control. Before disposal, they have to be tested via a leaching procedure and compared to waste disposal standards. In order to treat fly ash, the Ministry of Health and Welfare specified four treatments: 9Melting and solidification 9Solidification by cement 9Stabilisation using chemical agents 9Extraction with acid or other solvent After all standards have been passed, the treated fly ash could be disposed directly into sanitary landfill sites with other domestic wastes.

5.3.3 Utilisation Two fundamental concerns with utilisation applications are that 1) the physical properties of the material are appropriate for the intended application (i.e., bearing capacity, compaction, etc.), and 2) the application does not lead to environmental degradation. The latter situation relates mainly to the leaching of metals and salts from the ash, since the potential loading of ash within a fill application may pose a potential problem. In Europe, the materials are used as a civil engineering material, largely as base and sub-base for roadways. Each country has considered the environmental implications of these uses and developed guidelines for implementation. While the subject of utilisation is discussed in more detail later in the document, a brief discussion of existing regulations governing the use of residues is included here.

156 Canada As mentioned previously, although no major efforts have been devoted to utilisation in Canada, the Greater Vancouver Regional District has evaluated bottom ash for utilisation applications, and currently uses the material for construction of roadways within a landfill site. The bottom ash undergoes ferrous removal prior to leaving the Burnaby facility, but no other processing is done other than compaction during placement.

One of the major impediments to bottom ash utilisation is that there has been little economic incentive to divert materials from landfill. Should sufficient regulatory criteria be put in place to allow the use of bottom ash as a lightweight aggregate, it is likely that the practice would be considered for ash from some of the major facilities.

Denmark Although part of the bottom ash stream from incinerator facilities in Denmark has been used in sub-bases for roads, bicycle paths and parking lots since 1974, the first Danish utilisation requirements were not developed until 1983 (Statutory Order No. 568 of Dec. 6, 1983). Moreover, these requirements only applied to the use of small to moderate amounts of ash. Large scale applications (>30,000 tonnes or 5 m thickness) are regulated under the Environmental Protection Act (Disposal and Discharge Permit section). Additional guidelines for road sub-bases were developed in 1989 by the Danish Highway Department (Pihl et al., 1989 in Hjelmar, 1990). The Statutory Order is currently being reviewed. Ferrous material is removed from the ash by screening and then magnetic separation to generate an upgraded material for recycling purposes. The portion of the bottom ash stream which cannot be used is disposed in dedicated monofills.

A Danish testing protocol has been developed to determine the suitability of ash for utilisation based on chemical parameters (Hjelmar, 1990). The conditions include a pH >9 for a 1% slurry of the material, alkalinity of >1.5 eqv/kg, metals levels as determined from a HNO3 leach of Pb 99%). The first one applies a thermal treatment in a rotary kiln at about 400~ under oxygen deficient conditions, then copper salts are added as catalysts. A full scale facility is in operation (Schetter et al., 1990). A second process, the 3R Process, utilises the combustion chamber of the incinerator itself to decompose PCDD/PCDF in extracted and compacted filter ashes (Merz et al., 1989). All vitrification processes proposed for APC residues may also be appropriate for treatment of PCDD/PCDF as well.

320 Figure 8.27 Incinerator

Concentrations (TE) and Partitioning of PCDD/PCDF in a Modern

Based on the information given above, a modern MSW incinerator which is well operated and equipped with adequate APC devices is capable of meeting the most stringent emission regulations for PCDD/PCDF. In some European countries, this limit is 0.1 ng(TE)/Rm 3, however, even lower limits have been achieved during recent pilot plant studies ( 4.75 mm) fractions. The data shown in Table 9.12 indicate that for the fine fraction, mean percent losses ranged from 1.6 to 11.91. The coarse fraction mean values were 2.6 and 2.9. As with sorption, the fine fraction is more susceptible to expansive fragmentation compared to the coarse fraction. This is because bottom ash fine material is more porous than the coarse material. There is a wide variation in values for the fine fraction seen between facilities within the United States. It is not clear as to why this variation exists.

Figure 9.11 Bottom Ash Percent Fines as a Function of Time Percent

Passing,

%

..... H o u r l y

0

--

0

i

2

Average

Overall A v e r a g e

t.

P

~

~

L

_l

J

4

6

8

10

12

14

16

Sampling

Day

18

20

The vertical bars are the 95% confidence intervals After Eighmy et al., 1992

Abrasion Resistance The Los Angeles abrasion test measures the ability of an aggregate material to maintain its physical integrity under defined abrasive conditions. The test is conducted on two different size fractions, a coarse and a fine fraction, termed "B" and "C", respectively. The test is considered to be highly aggressive with respect to evaluating lightweight porous aggregate materials. Table 9.12 provides data on LA abrasion resistances for bottom ash B and C fractions from facilities from the United States. Typical percent losses observed for both fractions are around 40 to 45%. These values are considered to be high, however they are typical for porous lightweight aggregate materials.

362 Table 9.12 Bottom Ash Durability Country Facility

United States

Concord, NHc Dry Scrubber I d Dry Scrubber 3 d

Soundness % Lossa Fine Coarse Min Max Mean Median n Min Max Mean Median 2.63 10.38 14.32 11.91 11.48 4 2.51 2.76 2.63 . . . . 1.7 3.4 2.7 4 2.9 1.1 2.4 1.6 5 1.6 4.0

Country Facility n

" b

Concord, NH c Dry Scrubber 14 Dry Scrubber 24 Dry Scrubber34 Dry Scrubber34 ASTM C88. ASTM C131.

5

LA Abrasion, % Loss b C Fraction

B Fraction United States

n 4

Min

Max Mean Median

4 46.4 48.2 - 57.8 58.5

47.3 58.2

. . . . 5 57.6 61.0 - 46.0 61.8

. 59.6 54.9 c d

47.3 -

n

Min Max Mean Median

n Reference

2 4

42.6 44.2 43.4 40.4 40.7 40.6

43.4 -

2 E i g h m y e t al., 1992 2 LIRPB, 1992a

5

43.1 46.1 44.6 44.9 48.3 46.6

-

2 5

6

41.3 47.5 45.0

-

6

Original fraction less than 19 mm. Original fraction less than 50.8 mm.

9.1.5 Geotechnical Properties Many of the utilisation scenarios envisioned for bottom ash involve the use of bottom ash as an aggregate substitute subjected to compaction. Despite the potential problems of durability with bottom ash, bottom ash is a highly compactible material that upon compaction has high levels of E-modulus and strength. The fine fraction in bottom ash, the retentive capacity of bottom ash for holding water and the porosity of bottom ash mean that careful attention must be given to bottom ash water content prior to compaction.

Proctor Compaction The compactibility of a granular material is frequently assessed in the laboratory using Proctor compaction testing. Figure 9.12 shows a typical Proctor compaction curve with an optimum moisture content at maximum dry density. Table 9.13 provides data on bottom ash Proctor moisture optimums as well as maximum Proctor densities. Data are provided from facilities from the Netherlands, Sweden and the United States. As can be seen in the table, mean Proctor densities range from 1530 to 1739 kg/m 3. The minimum and maximum values that are observed are 1242 to 1838 kg/m 3 for all measurements. Good agreement is seen between facilities from the different countries. The geotechnical moisture content, at which maximum compaction occurs, tends to range from about 9.6% to 20%, with typical mean values of 13 to 16%. These moisture optimums are similar to those seen for gravelly sands in their ability to allow compaction to occur. There is good agreement between facilities from different countries with regard to moisture optimums that are observed.

363 Figure 9.12 Bottom Ash Proctor Compaction Curve Dry Density,

1.9

1000 k g / m 3

Typical Ash Zero Air Voids

1.6

--

8

I

I

,I

12

16

20

Moisture

After Eighmy et al., 1992

Content, %

Table 9.13 Bottom Ash Proctor Moisture and Proctor Density Compaction Country

Facility

Proctor Density (kg/m 3) Min

Max

Proctor Moisture (% W C )

Mean Median n Min Max Mean Median

Reference n

Netherlands AVI 1"

1,513 1,665

1,602

-

29 11.9 16.5

13.3

-

AVI 2"

1,543 1,630

1,573

-

26 10.9 16.0

13.0

-

16

AVl 3'

1,445 1,620

1,530

-

26 10.6 18.7

14.2

-

26

1,475 1,630 -

1,530 -

20 9.6 16.5 1 1,748 18 12.0 16.0 1,345 1 -

12.9 15.5

..... -

20 1 Hartl6n & Ro~lbeck, 1989

15.4 -

16.0 12.8

18 Eighmy et al., 1992 1 LIRPB, 1992a

16.0 14.6

-

21.3 -

16.6

Sweden

AVl 4" Maim6 ~

United States

Concord, NH c 1,619'""'1,838 ""'1,739 Dry Scrubber 1d -

.........

1,825

Dry Scrubber 2 d 1,242 1,298

1,271

-

Dry Scrubber 3 d 1,500 1,588

1,545

-

Dry Scrubber 3 d 1,550 1,580

1,566

-

-

2,463

Mass burn d

Standard Proctor. Standard Proctor.

-

-

c d

2 15.0 17.0 5 14.3 14.8 5 20.8 21.7 1 -

29 TAUW, 1988

2 5 5 1 Kosson et al., 1992

ASTM D1557 (Modified Proctor). ASTM D1557 (Modified Proctor).

The E-modulus can be evaluated for bottom ash materials as a function of Proctor compaction. Work by Hartl~n and Elander (1986) shows very high E-modulus values for ashes compacted in the fresh form and aged. The E-modulus values that are observed indicate that bottom ash is a strong aggregate material when it is in a compacted state.

364

Field Compaction Field compaction can be an aggressive, energetic process. Frequently, the compaction methods that are used in the field can break down particles in bottom ashes. Figure 9.13 shows how bottom ash particle size distributions become finer after field compaction efforts. The data, provided by Hartl~n and Rogbeck (1989), show that most full scale field compactors will fracture and fragment bottom ash and change the grain size distribution. At this time it is not clear if the degree of grain size redistribution is problematic with respect to civil engineering structural fill applications. Many bottom ash utilisation studies have shown that bottom ash can be successfully used as a compacted aggregate material in road sub-bases or in wind barriers and embankments. However, the fines content may require control as this influences frost susceptibility in cold climate applications.

Figure 9.13 Bottom Ash Particle Size Distribution after Field Compaction Siltl

"

I

sand

Gravel

.... I

Silt

0.06 -,.., r

0.2

0.6

2

90

C~.

80

./;y

V

~> 0

20

/M

70

e-

6

100

r i._

/

50

~

0 0.063

*~9

1 0 0 0.06

~

so

9

70

0 r

30

-~

20 10

0.5

I

Gravel

1

).2

0.6

4

Mesh Opening, mm

2

6

20

60

/,Y /,#"

*-~11 0.25

San~

,/

20 10

I

Grain Size d. in mm

Grain Size d. in mm

7 S

r

_

1

16

4

16

63

Mesh Opening, mm

2 months old

1 year old

The shaded area represents the original grain size distribution The solid line (A) shows the new grain size After Hartldn and Rogbeck, 1991

California Bearing Ratio (CBR) The CBR is a determination of the strength and stability of a compacted material. Values greater than 100% for CBR are seen in bottom ash. Table 9.14 provides information on CBR values at 0.1 inches and 0.2 inches for bottom ash samples obtained from facilities in either the Netherlands or the United States. Mean values seen at 0.1 inches range from 51.8 to 79.7% with minimum values at 22 and maximum values of 112.5 for all measurements. The CBR at 0.2 inches is higher. Typical mean

365 values are 39.0 to 154.5%, with minimum and maximum values ranging from 32.0 to 167.3% for all measurements. There is not good agreement between the data from different countries, but it is not clear why.

Table 9.14 Bottom Ash Penetration Resistance Country

Facility

CBR @ 0.1 Inches a Min

Max

CBR @ 0.2 Inches a

Mean Median n

Min

Max

Reference

Mean Median n

Netherlands AVI 1

24.0

65.0

52.0

-

29

32.0

76.0

62.4

-

29 T A U W , 1988

AVI 2

38.0

62.0

51.8

-

26

52.0

74.0

61.2

-

26

-

-

AVI3

22.0

42.0

31.7

AVI4

27.0

46.0

34.1

United

Concord, NH

63.0 112.5

States

Dry Scrubber 1

.

.

.

.

Dry S c r u b b e r 2

.

.

.

.

2

121.0 158.7 139.9

-

2

Dry Scrubber 3

.

.

.

.

5 122.7 167.3 154.5

-

5

Dry Scrubber 3

.

.

.

.

5

-

5

79.7

80.0

26 28.0

50.0

39.0

20

34.0

58.0

42.1

20

92.0

136.5 110.2

1

-

-

38.7

-

126.0

26 20

107.5 2 0 E i g h m y e t a l , 1 9 9 2 146.0

90.1

1 LIRPB, 1992a

Figure 9.14 shows how CBR varies as a function of time at the Concord facility. The data show that CBR exhibits some variability as a function of time.

Figure 9.14 Bottom Ash CBR as a Function of Time CBR, %

CBR

a t 2.54

mm Penetration

CBR '

9O

130 1 120

a t 5.08 m m P e n e t r a t i o n

@~

f" ...........

.

ll0t. -

--

70

i

i

100 I

Average ~ _ L

50 0

2

4

6

L

8

i

..... 95% C. I.

10

L___

12

S a m p l i n g Day

After Eighmy et al., 1992

~I___~L 14 16

i 18

80

70

I

0

Average

..... 05% C I

L

t

i

I

I

I

2

4

6

8

10

12

q9a m p l i n g

Day

14

16

18

,

366

9.1.6 Permeability The permeability of bottom ash, or its ability to transmit water via percolation, is an important component with regards to characterising the hydraulic regime to which bottom ash can be subjected. Because bottom ash is a well-graded material and can be compacted to high densities, it is expected that under compactive efforts the permeability of bottom ash will be quite low. Frequently, an assessment of the permeability of bottom ash is needed to model leaching of bottom ash, to model water balances of water moving through bottom ash and to assess the ability of bottom ash to freely drain. Utilising permeability testing apparatus, permeabilities that have been observed in bottom ash are usually in the low 106 cm per second range. Table 9.15 shows some bottom ash permeabilities obtained in studies conducted in both Denmark and Sweden. At maximum density, it appears that bottom ash permeability can range from about 0.2 to 10.0 x 106 cm/s. Such permeabilities are considered to be relatively low for wellgraded materials and reflect the presence of fine material which increases the tortuosity within bottom ash. Such low permeability values suggest that bottom ash may be subject to some infiltration but could also create some surface runoff.

Table 9.15 Bottom Ash Permeability Permeability 106 cm/s

Reference

-

3.5-4.4

Geoteknisk Institute, 1992

Malm5

0.2-10.0

Hartl~n & Elander, 1986

Country

Facility

Denmark Sweden

9.1.7 Influence of Combustor Type and Operation on Physical Characteristics There has not been a great deal of study conducted on the influence of combustor type and combustor operation on the physical properties of bottom ash. The comprehensive N ITEP program was the only large scale study that has been conducted to date that has looked at the influence of poor combustor operation and combustor type on ash characteristics. The only data that is available at this time is information on the loss on ignition content for a variety of facilities operated under both good and bad conditions.

As shown in Figure 9.15, two-stage systems operated either under good or bad conditions produce bottom ash with significantly higher LOI values than mass burn or RDF systems.

367 Figure 9.15 Influence of Combustor Type on Bottom Ash LOI LOI

30-

r... o ~

20-

tO O) O) 0 _J

10-

[;

I

!

I

I

0 2_Stage

Mass_Burn

RDF

9.1.8 Influence of Aging on Bottom Ash Physical Characteristics There have been some studies conducted in Sweden, Germany and the U.S. on the influence of aging on certain physical characteristics of bottom ash. In Sweden, it has been shown by Hartl~n and Rogbeck (1989) that the E-modulus of bottom ash will increase as bottom ash ages over time when compacted at optimum moisture under Proctor compaction testing. This increase in strength is attributable to the formation of mineralogical phases that increase particle interlocking within the bottom ash. Additional studies on aging in Sweden from bottom ashes at the Malmo facility have shown that when ash is aged for almost a year, the Proctor compaction characteristics are much better than when ash is freshly collected (Hartl~n and Elander, 1986). Again, aging is thought to increase the formation of certain mineralogical phases that increase the durability of the residue and interlocking characteristics of the particles in the residue. Studies in Sweden have also evaluated the influence of aging on the gross composition gradation of bottom ashes generated from the Malmo facility. There do not appear to be any significant differences between the nonmagnetic fraction, the glass fraction, the ceramic material, stone material and organic material in either fresh or aged fractions (Hartl~n and Lundgren, 1992).

368 Studies have been conducted in Germany to look at the influence of aging on a number of civil engineering properties. The data, presented by Vehlow (1992), show the influence of aging on leachable solids in bottom ash as bottom ash ages. The concentration of leachable solids in bottom ash decreases during aging. This is particularly true for facilities A and C (see Table 9.1). Facility B did not exhibit the same trends. The susceptibility to freeze/thaw fracturing has also been evaluated for aged materials in German facilities and the data suggests that the susceptibility to freeze/thaw erosion decreases with aging. This is particularly true again for facilities A and C. The data from facility B does not support this observation. Also evaluated in the German study was the raw density of aged material compared to fresh material at the three facilities. In all cases the raw density tended to increase with aging. This phenomenon is not presently understood.

9.2 PARTICLE MORPHOLOGY, MINERALOGY, AND ALKALINITY OF BOTTOM ASH Particle morphology, mineralogy and alkalinity of bottom ash play important roles in both the physical and chemical characteristics of bottom ash. The particle morphology of bottom ash is an important component in its physical characteristics and performance because of the angular nature of bottom ash particles. Bottom ash also tends to be a rough-textured material and this is an important property with regards to its physical performance. The mineralogy of bottom ash is thought to be important to understanding the leaching behaviour of bottom ash; however, the mineralogy also plays an important role in the compactibility and strength development of bottom ash as it ages with time. Finally, buffer capacity is an important component for both physical and chemical performance because of the role of the carbonate buffer system in bottom ash and the influence that has on strength development, particle aging and leaching.

9.2.1 Morphology Figure 9.16 provides some scanning electron microscopy micrographs and petrographic thin section micrographs of bottom ash particles. As can be seen in the SEM micrographs, bottom ash is an angular material. Slag-like material can be seen; the slag material is porous and contains vesicles. The petrographic thin section of bottom ash clearly shows that bottom ash possesses a high degree of internal porosity that is connected to the exterior of the particles. This vesicle porosity provides a large surface area for chemical reactions to take place and for leaching phenomenon to occur. As shown in Table 9.16, a number of researchers have looked at the specific surface area of bottom ash using BET absorption isotherms. Typically, bottom ashes have surface areas of 3 to 46 m2/g dry weight of bottom ash. These are considered to be very high degrees of surface area for a granular material. For instance, traditional

369 soils have surface areas that are orders of magnitude less than that. Mercury porosimetry is also used to look at internal pore diameters as can be seen in Table 9.16. A number of the pores in the material are considered to be quite small in nature. Values of less than a tenth of a micron are seen. The data also suggest that combustor type has an influence on the type of surface area and pore diameter that is found in bottom ash. The reader should refer to Chapters 12 and 13 for further discussion on the role of surface area in chemical leaching phenomenae.

Figure 9.16 SEM Micrographs (a,b) and Petrographic Thin Section Micrographs (c,d) of MSW Bottom Ash

370 Table 9.16 Bottom Ash Surface Area BET Country Facility Surface Area m2/g

Pore Diameter" IJm

Reference

RDF b 4.605 Gardner, 1991 PRF b 3.286 0.0947 Gardner, 1991 RDF b 9.469 0.0786 Gardner, 1991 RK-MB b 28.184 2.117 Gardner, 1991 Unknown 9.4-46.3 Theis & Gardner, 1990 MB b 3.2 0.0342 Kosson et al., 1992 Mercury porosimetry. RDF=Refuse-Derived Fuel, PRF=Processed Refuse-Derived Fuel, RK=Rotary Kiln, MB=Mass Burn

United States

In comparing the petrographic thin sections of bottom ash with the surface area and porosimetry data provided in Table 9.16, it is clear that the internal porosity that is connected to the exterior accounts for a great deal of the surface area measured by nitrogen BET absorption isotherms. Compared to most aggregates, bottom ash is considered to be a light-weight porous aggregate with more angularity and more surface roughness and textures than many traditional aggregates.

9.2.2 Mineralogy The mineralogical characteristics of bottom ash play a very important role in the leaching behaviour of bottom ash. It is estimated that bottom ash contains numerous mineral phases. Such diversity complicates our understanding of the leaching behaviour of bottom ash and more research needs to be conducted on the role of mineralogy in bottom ash aging and strength development. Nevertheless, there are at least four studies that have been conducted that have examined the mineralogy of bottom ash. The studies have been conducted by St~mpfli (1992), Vehlow et al. (1992), Kirby and Rimstidt (1993) and Eighmy et al. (1994). All four of these studies have used rigorous procedures employing x-ray powder diffraction (XRPD) and other methods as precise procedures for estimating the nature of the mineral phases. St~mpfli (1992) has examined bottom ash for the presence of those mineral phases that are associated with strength development as bottom ash ages. St~mpfli used XRPD to determine the mineralogy. Minerals identified include SiO2, CaCO3, Fe304, Fe203, Fe, FeO, Ca~,I(OH)7.6.5 I--120,Na2Si20~, and CaSO4. Others are shown in Table 9.17.

371 Table 9.17 Mineral Phases in Bottom Ash (in relative order of decreasing abundance) St~impfli (1992)b Vehlow et al., (1992)o Kirby and Rimstidt Eighmyet al. (1993)d (1994)e SiO2 CaCO3 Fe304

Fe304 SiO2 (Ca, Na)2(AI,Mg)(Si,AI)207

SiO2 CaSO4 o 2 H 2 0 3(AI203)~ TiO2

Fe203 Feo

CaCO3 KAISi308

Fe203 FeO

FeAI204 SiO2

FeO

NaAISi308

CaSO4

CaG(PO4)2

Ca2AI(OH)T.6.5H2 O

CaAI2Si208

KCI

Fe203

Na2Si2Os CaSO4 (Ca, Na)(Al,Si)2Si8 NaAISi308

FeCr204 Ca(Mg,Fe)Si206 Fe2SiO4

NaCI

CaSO4 CaO AI(OH)3

Ca2AI2SiOT MgCa2Si207 Fe304

Cr203 Fe203 CaMgSiO4

NaCI ZnCI2 NaAISi308

AI203 Ca(OH)2 CaSO4

AI2SiOs TiO2

b Basedon XRPD c Basedon petrographyand XRPD

Based on XRPD Basedon petrography,XRPD,XPS, SEM/XRM

Vehlow et al. (1992) have conducted extensive characterisations of bottom ashes from three facilities in Germany. They used XRPD and petrography. Data are presented in Table 9.17. The principle phases found in ash from the German facilities are glass, magnetite, quartz, melilite and feldspar. A number of other minor phases were also identified. Agreement was seen in the relative presence of major phases amongst the three facilities. Vehlow et al. (1992) also looked at aging effects. Kirby and Rimstidt (1993) studied bottom ashes containing small quantities of fly ash. They used XRPD as well. Principle minerals include (% abundance) Fe203 (3.7%), CaCO3 (3.5%), NaCI (0.5%), SiO2 (2.3%), magnetic spinel (3.5%), TiO2 (1.1%), and CaSO4 o2H20 (1.8%). The majority of the non-LOI mass of the sample was amorphous glass and minerals present below the detection limit for XRPD. Table 9.17 provides further information. Eighmy et al. (1992) examined the characteristics of bottom ash using XRPD, petrography, SEM/XRM and surface microanalytical techniques for samples from a U.S.

372 facility. The bottom ashes were ground and separated using magnetic and density gradient separation procedures. Table 9.17 provides a summary of the data. Many of the phases found in the U.S. bottom ashes are similar to the ones identified by the other studies.

9.2.3 Alkalinity The buffer capacity of bottom ash is an important component in the leaching characteristics of bottom ashes. The acid neutralising capacity of the residue is a measure of how many milliequivalents of nitric acid are required to reduce the pH of one gram of residue to a value of 4.3. The endpoint of the titration can vary. Some researchers use a value of 7.0, while others use the more traditional carbonate alkalinity endpoint. To put this measure into perspective, one gram of residue would need to be leached with 45 litres of acidic precipitation to reduce the pH from 12.0 to 7.0. Table 9.18 provides some information on the acid neutralising capacity as well as the initial pH or the inherent pH of bottom ashes for samples collected from Canadian and U.S. facilities. Typically, bottom ash has an initial pH ranging from 10.5 to about 12.2. This is in part due to the presence of calcium hydroxides produced from CaO hydrolysis in the bottom ash. The acid neutralising capacity of bottom ash ranges from about 1.2 to 4.1 milliequivalents per gram. This means that bottom ash is reasonably well-buffered. Such buffering capacity indicates that bottom ash can moderately resist changes in pH.

Table 9.18 Bottom Ash pH and Acid Neutralising Capacity Country

Facility

Canada

LVH SWARU QUC

Initial pH

.

ANC, meq/g Reference

10.20

3.05

Sawell et al., 1989b

-

4.11

Sawell et al., 1989a

11.39

2.15

Sawell and Constable, 1988

United States Concord, NH 10.5-12.2

1.2-3.0

Eighmy et al., 1992

Figure 9.17 provides a typical titration curve for bottom ash. The data indicate that there are a number of locations in the titration curve where a slight degree of buffering takes place. These buffers tend to occur at a pH of around 10, 8 and 5. Such locations for buffers are attributable to the carbonate system. Figure 9.18 shows the change of botom ash acid neutralising capacity as a function of time for bottom ashes collected from the Concord facility (Eighmy et al. 1992). The acid neutralising capacity is relatively variable over time.

373 Figure 9.17 Bottom Ash Titration Curve I0.000 8.000

Ave A N C - 2.1 m e q / g

6.000 "i-

4.000 2.000 0.000

. . . .

I

i

J

,

1.0

0.0

9

i

. . . .

!

2.0

. . . .

!

3.0

. . . .

I

4.0

. . . .

5.0

!

. . . .

!

6.0

. . . .

i

7.0

. . . .

8.0

m e q / g dry bottom esh After Eighmy et al., 1992

Figure 9.18 Bottom Ash ANC as a Function of Time 4.5 0

First Hour 9 Second Hour Z~ Third Hour A Fourth Hour 9 Daily Composite i l l

4.0 ol

3.5

O" Q)

E 3.0

9

0 z 10,000 mg/kg), some are present as minor constituents (>1,000 but 10,000 mg/kg), minor constituents (>1,000 mg/kg but 1000,000 mg/kg) Measured in APC Residues from Mass Burn Incinerators Residue

Element

Mean (mg/kg)

Median (mg/kg)

25-75 percentile range (mg/kg)

n

FA

Ca CI Si Mg Fe AI K Na Zn S Pb

107,000 74,000 160,000 15,000 25,000 71,000 36,000 31,000 28,000 26,000 11,000

107,000 50,000 170,000 15,000 23,000 73,000 34,000 29,000 22,000 27,000 7,800

95,000 - 120,000 40,000 - 102,000 130,000 - 180,000 14,000 - 17,000 18,000 - 33,000 59,000 - 81,000 30,000 - 41,000 23,000- 38,000 16,000 - 35,000 21 000 - 33,000 6,300- 15,000

20 24 14 15 20 18 19 17 26 20 25

SP/DP

Ca CI Si Mg Fe AI K Na Zn S Pb

230,000 180,000 69,000 9,400 12,000 26,000 23,OOO 17,000 15,000 15,000 5,400

220,000 160,000 63,000 8,800 9,100 19,000 24,000 15,000 16,000 17,000 5,600

180,000- 280,000 91,000- 220,000 51,000 - 92,000 7,400 - 12,000 63,000 - 11,000 15,000- 29,000 15,000 - 31,000 12,000 - 20,000 12,000- 18,000 8,200 - 21,000 4,100 - 63,000

19 23 12 16 19 27 18 16 28 18 27

WP

Ca

150,000 36,000 78,000 75,000 54,000 28,000 3,900 1 900 31 000 4 400 11 000

160,003 38,000

87,000- 200,000 26,000 - 47,000

3 4

Cl Si Mg Fe AI K Na Zn S Pb FA: Fly ash WP: Wet sludge without FA

SD/DP:

n:

-

-

1

36,000 45,000 25,000 2,300 1,700 29,000

19,000 - 170,000 20,000- 97,000 21,000- 39,000 810 - 8,600 720- 3,400 15,000 - 45,000

3 3 3 3 3 12

-

2,700

- 6,000

2

9,700 4,400- 19,000 12 Semi-dry/dry APC process products with fly ash Number of residues analysed

467 Klingspor et al., 1989;). This trend is illustrated in Figure 11.10 by the increase in chloride concentration of ESP ash with decreasing flue gas temperatures. The data is taken from a study at a mass burn incinerator and shows a marked difference in chloride concentrations with the inflection point between 220~ and 230~ (Sawell and Constable, 1988). It is important to note that there was no lime injection prior to the ESP unit.

Figure 11.10 Influence of Temperature on Chloride Concentrations in ESP Ash 250000

E

rl

EL C~

13 PT5 GOOD

E

.2

2oo0oo

-

150000

-

o E E O (-J

~

O ..E (,_)

13 PT9 GOOD

~ !

100000 190

200

ESP

PT4 POOR

!

I

!

210

220

230

I"1 PT14. POOR

24-0

TemperGture (~

From Figure 11.9 it can be seen that calcium and chloride are the only major elements which are more abundant in SP/DP than in FA. The content of very soluble calcium chloride, which may account for up to 60 percent of the total mass of semi-dry/dry APC system residues (without prior removal of fly ash), is responsible for many of the difficulties involved in the management of these residues. Not only do the very high concentrations of calcium chloride in the leachate pose a risk to potable water, but it may also increase the solubility of other potential contaminants such as trace metals (see Chapter 13). Furthermore, the solubility and thermal instability of the calcium chloride are serious obstacles to solidification and thermal stabilisation of the residues without prior removal of the soluble salts (see Chapters 18 and 19). A substantial amount of the sulphur in APC residues is present as sulphate and sulphite. Between 46,000- 80,000 ppm of SO42- and 13,000 - 35,000 ppm of SO32 have been measured in semi-dry and dry APC system residues, and 110,000 ppm of SO42 and 9,000 ppm of SO32-in a wet APC system residue mixed with fly ash (Hjelmar, 1992). The sulphite is thermodynamically unstable under oxidising conditions, and if the APC residue is exposed to oxygen (e.g. atmospheric air), will gradually be oxidised to sulphate. In wet scrubber residues, part of the sulphur content is present in the form of organic

468 sulphides (e.g. trimercaptotriazine, TMT). The long-term stability of these sulphides is not known. Both Pb and Zn are present as major constituents in APC system residues. Because of its increased solubility at high pH values, high ionic strength and high chloride concentrations, Pb is of particular concern in relation to disposal and utilisation of APC system residues. Figure 11.11 presents box plots depicting the concentrations of the minor elements in APC system residues (FA, SP/DP and WP) from mass burn incinerators. Table 11.15 gives the mean and median values as well as the 25-75 percentile ranges of the concentrations of the minor components Ti, Mn, Ba, Sn and Cu for the three types of residues.

Table 11.15 Concentrations of Minor Elements (1,000- 10,000 mg/kg)Measured in APC Residues from Mass Burn Incinerators Residue

Element

Mean (mg/kg)

Median (mg/kg)

25-75 percentile range (mg/kg)

n

FA

Ti Mn Ba Sn Cu

8,700 1,300 1,700 1,400 1,200

8,700 1,200 1,700 1,500 1,100

7,500- 9,400 1,000 - 1,600 940 - 2,600 890 - 1,800 930 - 1,300

17 19 18 15 25

SP/DP

Ti Mn Ba Sn Cu

3,300 480 540 890 710

3,200 440 450 840 630

2,600 - 4,400 280 - 680 320 - 660 770- 1,000 490 - 860

17 19 18 15 25

2,600 9,100 460 400 1,200

2,200 10,000 200 900

1,400 - 4,300 5,400 - 12,000 87 - 670 340 - 450 760- 1,700

3 3 11 2 12

WP

FA:

Ti Mn Ba Sn Cu Fly ash

SD/DP:

Semi-dry/dry APC process products with fly ash

WP:

Wet scrubber products without fly ash

n:

Number of residues analysed

Figure 11.I 1 Minor Element Concentrations in Fly Ash (FA), Semi-DrylDry APC Products with Fly Ash (SPIDP) and Wet Scrubber Products Without Fly Ash (WP-FA)

15000

m

ioooo

1

Y

\

m

E

5000

Copper, Cu

Tin, Sn 2500

Barium, Ba

Manganese, Mn

Titanium. T I

1 3000 4000

I

,OoO

1

470 Inorganic carbon in the form of carbonate is also one of the minor elements. Total concentrations between 16,000 - 33,000 ppm for CO32 in SP/DP and a value of 19,000 ppm for CO32 in WP have been reported (Hjelmar, 1992). Carbon is also present in APC system residues as elementary C (soot or char) carried over from the boiler. In addition, activated carbon may be injected with the sorbent in some dry/semi-dry APC systems in order to enhance mercury adsorption.

Trace Elements (< 1,000 mglkg): Hg,Cd,Sb,Cr, Sr, Ni,As,V,Ag,Co, Mo,Se Figure 11.12 presents box plots showing the distribution of some trace elements in APC system residues (FA, SP/DP and WP) from mass burn incinerators. Table 11.16 shows the mean and median values as well as the 25-75 percentile ranges of the concentrations of the trace elements Hg, Cd, Sb, Cr, Sr, Ni, As, V, Ag, Co, Mo and Se for the three types of residues. The concentration of mercury is substantially higher in WP than in SP/DP, which in turn has a higher concentration of mercury than FA. Trimercaptotriazine (TMT) which is most commonly used for wet scrubber wastewater treatment is particularly effective for removal of mercury and is ultimately concentrated in the sludge. Several facilities equipped with dry or semi-dry APC systems inject sodium sulphide, or as mentioned above, activated carbon with the sorbent to increase the sorption of mercury vapour. Without mercury control, mercury tends to condense out as Hg2CI2 (mercuric II chloride) (Metzger and Braun, 1987). Mercury in this form can undergo either reduction or methylation on fly ash, and that elevated temperatures can greatly increase the speed of the reduction reaction (Lindquist et al., 1986). Nagase et al., (1986) observed that methylation of Hg2CI2 can occur at normal temperatures on fly ash. Several studies have been conducted on the removal efficiency of mercury from flue gas based on temperatures at the outlet of the APC system (e.g., Moiler and Christiansen, 1985; Clarke, 1986; Carlsson, 1986; Environment Canada, 1986). All of the studies demonstrated that the increased efficiency of mercury removal was achieved (>91% capture) at temperatures below 150 - 160~ At temperatures over 200~ mercury removal efficiency was negligible, if not nonexistent. However, the use of activated carbon or sodium sulphide has been demonstrated as effective control reagents for mercury (Guest and Knizek, 1991). Sodium sulphide injection results in effective formation of stable HgS. Consequently, mercury (as well as sulphate) concentrations are increased in the residues. Conversely, it has been speculated that mercury sorbed onto activated carbon is not as stable, since it is susceptible to reduction by carbon. Although this has not been confirmed, further study into the phenomenon should be conducted to ensure that there is no substantial release of elemental mercury into the atmosphere through reduction, or methylation reactions.

Figure 11.12 Trace Element Concentrations in Fly Ash (FA), Semi-DrylDry APC Products with Fly Ash (SPIDP) and Wet Scrubber Products without Fly Ash (WP-FA)

Antinony, c d

Cnroniun, c r

. Y

a

1000

Vanadium, V

iOOD

400 200

S i l v e r . ~g 120 1

C O M l t . CO

ioo

1

472

T a b l e 11.16 T r a c e Elements ( pH=p~,the surface would adsorb cations. Table 13.15 depicts some PH=pcfor various adsorbent mineral phases.

561 Sorption phenomena are usually modelled using empirical, experimentally determined sorption constants based on solute activity or using mechanistic explanations of the electrostatic interactions that occur at the particle surface. Both approaches can be modelled in the modelling programs described in Chapter 15.

Table 13.15 Estimates of pHD=e for Various Minerals Mineral

pHDzc

y-AI203

8.5

Anatase (TiO2)

5.8

Birnessite (5-MnO2)

2.2

Calcite (CaCO3)

9.5

Corundum (a-AI203)

9.1

Goethite (a-FeOOH)

7.3

Hematite (a-Fe203)

8.5

Magnetite (a-Fe304)

6.6

Rutile (TiO2)

5.8

Quartz (a-SiO2) 2.9 Adapted from Davis and Kent, 1990 with permission from the Mineralogical Society of America

13.5.2 Activity-Based Sorption Models The first activity-based sorption model is based on the distribution coefficient, Kd (Allison et al., 1990). Using the convention of M as a metal and SOH as a hydroxylated surface sorption site, consider the following reaction depicting m sorbing to the surface site: SOH + M -

SOH" M

(13.75)

The ratio of sorbed metal concentration to the total analytical metal concentration in solution at equilibrium is the distribution coefficient. It is analogous to an equilibrium constant: Kd = [SOH" M] [M]

(13.76)

562 It is more appropriate to examine the Kd relationship based on the activity of participating aqueous metal solute: K da c t _ -

By convention [SOH

{SOH" M}

(13.77)

{i}

9 M] = {SOH ~ M} and equation (13.77) becomes: act_

Kd

-

[SOH" M] u [M]

(13.78)

Many Kd"= values are tabulated in the sorption review document prepared by Rai and Zachara (1984). The second approach that employs activity in an empirical way to depict sorption is the Langmuir adsorption model (Allison et al., 1990). Again, using the SOH and M terminology, consider the following reaction: SOH + M ,= S O H - M

(13.79)

where at equilibrium K Lact

_

{SOH

-

{M} {SOH}

9M }

(13.80)

Conventionally, the Langmuir constant is derived experimentally using various quantities of SOH and M. To place ~"= into the more familiar context of the Langmuir adsorption isotherm, a mass balance on surface sites is needed (Allison et al., 1990): [SOH]T = [SOH

9 M] + [SOH]

(13.81)

Combining equations (13.80) and (13.81) produces: K act

[SOH

9 M] =

L [SOH]T Ya[M] I~"

act

1 + "L

(13.82)

Yi[ M]

The only difference between Kda~ and ~a~t is that the Langmuir equation assumes a finite concentration of SOH. Values for ~"~ can be found in Rai and Zacchara (1984).

563 The third activity-based empirical sorption model is the Freundlich model (Allison et al., 1990). Again using the SOH and M terminology, consider the following reaction: SOH + l/nM = SOH. M

(13.83)

where at equilibrium Kfact =

{SOH 9M} {M} TM {SOH}

(13.84)

Imposing the convention that {SOH ~ M} = [SOH ~ M], equation (13.84) becomes: [SOH

9M] = Kfact {MM+}TM

(13.85)

The 1In term is a mass action stoichiometric coefficient related to M. Kf"ct is similar to Kd~ if n=l. Kfact differs from ~act in its implicit assumptions about an unlimited supply of unreacted surface sites at equilibrium. Kf"~tvalues can be found in Rai and Zacchara (1984). The fourth empirical, activity-based sorption model is the ion exchange model (Allison et al, 1990). Again using the SOH terminology, but denoting the exchangeable metal as M and the sorbing metal as M2, consider the following SOH- M 1 - M 1 § M 2 ,, S O H - M 2

(13.86)

where at equilibrium, Kex =

{M1}{SOH'M 2} {M2}{SOH'M 1}

(13.87)

K.x differs from the other three constants by assuming a substitution reaction occurs at SOH. K,x values are found in Rai and Zacchara (1984). There are no conventions as to the applicability of these four empirical models (Allison et al., 1990). When modelling sorption processes, all four models can be tested (provided appropriate constants are available). The literature does suggest that mechanistic models based on electrostatic considerations do a better job at modelling sorption (Allison et al., 1990); frequently parameters for these models are not available (as discussed below).

564

13.5.3 Electrostatic Surface Complexation Models There have been a number of attempts to model adsorption to mineral surfaces while taking into account electrostatic interactions between charged surfaces and solutes. The models explain how both cations and anions adsorb as a function of pH, adsorbent site density and ionic strength (Westall and Hohl, 1980). Models such as the constance capacitance model (CCM) and the diffuse double layer model (DLM) were developed (Davis and Kent, 1990). A third model, the triple layer model (TLM), was developed to have multiple adsorption planes on the mineral surface to allow for outer sphere as well as inner sphere complexes to form (Leckie, 1988). The TLM is viewed as most applicable and is presented here. The TLM is schematically depicted in Figure 13.18 (Leckie, 1988). As described by Evans (1989), tightly bound inner sphere complexes reside in the inner or surface plane, ~. (or cx plane). Outer sphere complexes reside in the adjacent plane, )~ (or 13 plane). Noncomplexed species reside in the diffuse layer, A,~(or d plane). To maintain electroneutrality, the charge density, o, must equal the intrinsic charge density of the mineral such that:

(13.88)

Oint + Ois + Oos + 0 d = 0

Figure 13.18 Depiction of the Triple Layer Model % ~r=

o'p

I I I

Od

I I I

NO~

§

I

-r" ?~

O~b*....

0

~:"

0

~:;!

OebOH

(I)

NO~ Na* NO~

NO~

I

I

I

I

I

I

I

NO 3

pb 2+ O :Z~

....

~

I

N

....

,Np

....

,"9;

i"L;: Ol'

....

l~b 2.

~L~! a

....

Pt~OH§

~'#

, |

a~

NO~

I~a§

I

~--~-.~ O H +

Na* NO~ NO 3

N% pb 2+

NO3

CI_ ,, J

13 immobile layer

d diffuse

layer

Reprinted with permission from Leckie, 1988. Copyright Lewis Publishers, an imprint of CRC Press, Boca Raton, Florida. 9

565

Hayes (1987) has depicted the types of binding mechanisms that can occur in both the inner and outer spheres (Figure 13.19). The figure shows various inner sphere and outer sphere complexation reactions that can occur.

Figure 13.19 Schematic Depiction of Coordinative Surface Complexes and Ion Pairs at Oxide Surfaces Metal

Oxygen

Other Examples

C~c,-b ~

",v..,,,>Water '~"" Molecules

C~a~1b

t3

I-. ~-. No;. ClO,-

Na* K + 2+ 2. , , Ca , Mg

uter-Sphere Complexes

c~,L co;k

"O"-~>__O_

pb.

Cu

f Divalent Transition Metal Ions

Monodentate

Divalent Transition Metal Ions

Bidentate

/ Inner-Sphere

"O~~

U~ap~exe s

F

,,O-'- H P

OH

Mononudear

SeO~;,~02

Binuclear

From Hayes, 1987 with permission of the author

566 Consider the following reaction for the monovalent metal ion M § (Allison et al., 1990): SOH

+

+

H s + M s ,- ( S O . M )

-

(13.89)

where SOH and Ms+ are the same surface binding site and sorbing metal and Hs§ is the sorbed proton that must deprotonate from SOH to allow for formation of the sorbed complex SO 9M. By convention, {H~} = {H *} [e-~~

(13.90)

{ms} = {m *} [e -YI~FIRT]

(13.91)

and +

where e "~F/RT is the Boltzmann factor for either the a or 13 planes depicted in Figure 13.19. Equations (13.86) through (13.88) can be written as an equilibrium expression (Allison et al., 1990): K = {SO

9M} {H *} [e-~~

(13.92)

{SOH} {M *} [e-~I3F/RT]

Other forms of equation (13.89) can be provided for a hydrolysis reaction of the type (Allison et al., 1990): SOH + M 2+ § H20 - 2H~ - S O . MOH

(13.93)

producing, K = {SO

9MOH} {H +}2 [e-I~~

2

{SOH} {M 2+} {H20 } [e-~I]F/RT]2

(13.94)

A similar approach can be taken for a sorbing monovalent anion (Allison et al., 1990): +

SOH + A s- + H s ,, SOH 2 A 9

(13.95)

producing, {SOH 2 A} 9 [e-~IBF/RT] K

._.

{SOH} {A-} {H *} [e-I~~

(13.96)

Finally, a similar approach can be taken for a sorbing divalent anion (Allison et al., 1990):

567 t

SOH + A 2- + H s =* SOH 2 A 9

(13.97)

producing K

=

{SOH 2 A-} 9 [e-e"F/RT]2 {SOH} {A 2-} {H +} [e-~oF/Rm]

(13.98)

The geochemical model MINTEQA2 has the capability to model sorption using estimated parameters for the TLM as well as the CCM and DLM. The TLM model has been widely used to model adsorption of cations and anions (Davis and Kent, 1990). For adsorption to oxides, Davis and Leckie (1978, 1980), Balistrieri and Murray (1982), Hsi and Langmuir (1985), Catts and Langmuir (1986), LaFlamme and Murray (1987), Zachara et al. (1987), Hunter et al. (1988), and Zachara et al. (1987) have successfully used the model. It has also been applied to non-hydrous oxide minerals like quartz, titanium and clay (Shuman, 1986).

13.5.4 Adsorption Data Davis and Kent (1990) have compiled some interesting data as to how cations and anions adsorb to mineral surfaces. As shown in Figure 13.20, there is a narrow pH range where a cation or anion goes from near zero adsorption to high levels of adsorption. This adsorption edge occurs at pHads, the pH where significant sorption occurs, which is close to the Prize:. Cations adsorb at high pH by forming inner sphere complexes with the deprotonated hydroxyl functional groups. Anions adsorb at low pH when forming inner sphere complexes with protonated functional groups.

13.6 A UNIFIED APPROACH TO LEACHING The information compiled in this chapter allows us to assemble an approach to characterising the leaching process. Understanding fundamental leaching behaviour of a residue such as ash requires the consideration of many factors (Figure 13.21). The speciation of the elements in the solid phase plays a fundamental role in controlling the nature of the leachate. This can then be related to that fraction of an element that is available for leaching. Particle morphology, porosity, and diffusion pathlength are also critical in assessing the role of diffusion in controlling reactions. Attempts to characterise those leaching processes that are kinetically based or thermodynamically based is an additional approach that is needed. The thermodynamic mechanisms can be modelled with geochemical codes. Additional data can be gleaned by conducting leaching studies to assess the effects

568 of pH, Eh and ligands on dissolution phenomena. The processes surrounding sorption cannot be ignored; these studies can be compared to the various sorption models that are presently available. Finally, the role of the L/S ratio and time must be considered. Figure 13.20 Adsorption Edges for Various Cations and Anions

From Parks, 1990 with permission of the Mineralogical Society of America

Now that these concepts have been explained, they need to be applied. The next chapter sets out various types of leaching tests which can be performed to determine certain characteristics of ash under specific sets of leaching conditions.

569 Figure 13.21 Schematic of Fundamental Leaching Behaviour

Available

Fraction Particle

Chemical Speciation

Therm odynamics

Morphology

FUNDAMENTAL LEACH IN G BEHAVIOUR

Kinetics

Influence of LS, Time

Influence of pH, pE & Ligands Sorption

570 REFERENCES

Allison, J.D., D.S. Brown and K.J. Novo-Gradac. MINTEQA2./.PR.0DEFA2.....A Geochemical Assessment Model for Environmental Systems: Version 3.0 User's Manual. Environmental Research Laboratory, U.S. EPA, Athens, GA, 1990. Baes, C.F. and R.E. Mesmer. The Hydrolysis of Cations. John Wiley & Sons, New York, 1976. Balistrieri, S.L. and J.W. Murray. The Adsorption of Cu, Pb, Zn, and Cd on Goethite from Major Ion Seawater. Geochim. Cosmochim. Acta 46, pp. 1253-1265, 1982. Belevi, H. and P. Baccini. Long-Term Assessment of Bottom Ash Monofill Leachates. In Proceedinas of the International Conference on Municipal Solid Wa.ste .C.ombustion. April 11-14, Hollywood, FL, USA, 1989. Bemer, R.A. Rate Control Of Mineral Dissolution Under Earth Surface Conditions. Am. J. Sci. 278, pp. 1235-1252, 1978. Berner, R.A. Kinetics of Weathering and Diagenesis. In Kinetics of Geochemical Processes (A.C. Edited by A.C. Lasaga and R.J. Kirkpatrick. Mineralogical Society of America, Washington, D.C., p. 111, 1981. Blum, P.J. and A.C. Lasaga. Monte Carlo Simulations of Surface Reaction Rate Laws. In Aquatic Surface Chemistry: Chemical Processes at the Particle-Water Interface Edited by W. Stumm. John Wiley and Sons, NY, p. 255, 1987. Boynton, R.S. Chemistry and Technolo.qy of Lime and Limestone. John Wiley and Sons, NY, 1990. Brookins, D.G. Eh-pH Diagrams for Geochemistry. Springer-Verlag, Berlin, 1988. Busenberg, E. and A.B. Plummer. The Kinetics of Dissolution of Dolomite in 002-H20 Systems at 1.5 to 65~ and 0 to 1 atm pCO2. Am. J. Sci. 282, pp. 45-78, 1982. Butler, J.N. _Solubility and pH Calculations. Addison-Wesley, Reading, MA, 1964. Casey, A.B. and A.B. Bunker. Leaching of Mineral and Glass Surfaces. In MineralWater Interface Geochemistry Edited by M.F. Hochella, Jr. and A.F. White. Mineralogical Society of America, Washington, D.C., p. 397, 1990. Catts, A.B. and A.B. Langmuir. Adsorption of Cu, Pb and Zn onto birnessite (6-MnO2). J. Appl. Geochim 1, pp. 255-264, 1986.

571 Cole, D.R. Theory and Application of Adsorption and Ion Exchange Reaction Kinetics to in situ Leaching of Ores. In Leachin.q and Diffusion in Rocks and Their Weatherin.(:i Products. Edited by S.S. Augustithis. Theophrastus Publishers, Athens, p. 3, 1983. Comans, R.N.J., H.A. van der Sloot and P.A. Bonouvrie. Speciatie van Contaminaten Tijdens Uitlo.qin.qvan AVI-Bodemas. Concept Eindrapport ECN-CX-93-XXX, April 1993. Davis, J.A. and J.O. Leckie. Surface Ionization and Complexation at the Oxide/Water Interface. I1. Surface Properties of Amorphous Iron Oxyhydroxide and Adsorption of Metal Ions. J. Colloid Interface Sci. 67, pp. 90-107, 1978. Davis, J.A. and J.O. Leckie. Surface Ionization and Complexation at the Oxide/Water Interface. 3. Adsorption of Anions. J. Colloid Interface Sci. 74, pp. 32-43, 1980. Davis, J.A. and D.B. Kent. Surface Complexation Modelling in Aqueous Geochemistry. In Mineral-Water Interface Geochemistry Edited by M.F. Hochella, Jr. and A.F. White. Mineralogical Society of America, Washington, D.C., p. 177, 1990. de Groot, G.J., H.A. van der Sloot and J. Wijkstra. Leaching Characteristics of Hazardous Elements from Coal Fly Ash as a Function of the Acidity of the Contact Solution and the Liquid/Solid Ratio. In Edited by P.L. C6t6 and T.M. Gillian.ln Environmental Aspects of Stabilization and Solidification of Hazardous and Radioactive Waste ASTM STP 1033, ASTM, Philadelphia, PA, pp. 170-183, 1987. Drever, J.l. The Geochemistry of Natural Waters. Prentice-Hall, Englewood Cliffs, NJ, 1988. Dudas, M.J. Long-Term Leachability of Selected Elements from Fly Ash. Environ. Sci. Technol. 15, pp. 840-843, 1981. Eighmy, T.T., S.F. Bobowski, T.P. Ballestero and M.R. Collins. Theoretical and Applied Methods of Lead and Cadmium Stabilization in Combined Ash and Scrubber Residues. In proceedin,qs of the Second International Conference on Municipal Solid Waste Combustor Ash Utilization. Edited by W.H. Chesner and T.T. Eighmy. November 8-9, Arlington, VA, p. 275, 1990. Evans, L.J. Chemistry of Metal Retention by Soil. Environ. Sci. Technol. 23, pp. 10461056, 1989. Feitknecht, W. and P. Schindler. Solubility Constants of Metal Oxides, Metal Hydroxides and Metal Hydroxide Salts in Aqueous Solution. Butterworths, London, 1963. Felmy, A.R., D.C. Girvin and E.A. Jenne. MINTEQ-A Computer Pro,qram for Calculatin,q Aqueous Geochemical Equilibria. EPA-600/3-84-032, U.S. EPA, Athens, GA, 1984.

572 Fruchter, J.S., D. Rai and J.M. Zachara. Identification of Solubility-Controlling Solid Phases in a Large Fly Ash Field Lysimeter. Environ. Sci. Technol. 24, pp. 1173-1179, 1990. Furuichi, R., N. Sato and G. Okamoto. Reactivity of Hydrous Ferric Oxide Containing Metallic Cations..Chimia 23, pp. 455-463, 1969. Garrels, R.M. and C.L. Christ. Solutions, Minerals, and Equilibria. Harper and Row, New York, 1965. Giovanoli, R. J.L. Schnoor, L. Sigg, W. Stumm and J. Zobrist. Chemical Weathering of Crystalline Rocks in the Catchment Area of Acidic Ticino Lakes, Switzerland. Clays Clay Min 36, pp. 521-529, 1989. Grandstaff, D.E. Some Kinetics of Bronzite Orthopyroxene Dissolution. Geochim. Cosmochim. Acta 41, pp. 1097-1103, 1977. Guggenheim, E.A. Applications of Statistical Mechanics, Clarendon Press, New York, 1966. Harvie, C.E., N. Mr and J.H. Weare. "The Prediction of Mineral Solubilities in Natural Waters: The Na-K-Mg-Ca-H-CI-SO4-OH-HCO3-CO2-H20 System to High Ionic Strengths at 25~ ''. Geochim. Cosmochim. Acta 48, pp. 735-751, 1984. Harvie, C.E. and J.H. Weare. The Prediction of Mineral Solubilities in Natural Waters: the Na-K-Mg-Ca-CI-SO4-H20 System from Zero to High Concentration at 25~ Geo.chim. Cosmochim. Acta 44, p. 981-987, 1980. Hayes, K.F. Equilibria, Spectroscopic and Kinetic Studies of Ion Adsorption at the Oxide Aqueous Interface. Ph.D. Dissertation, Stanford University, Palo Alto, CA, 1987. Helgeson, H.C. Thermodynamics of Hydrothermal Systems at Elevated Temperatures and Pressures. Am. J. Sci. 267, pp. 729-804, 1969. Hem, J.D. Equilibrium Chemistry of Iron in Groundwater. In Principles and Applications of Water Chemistry Edited by S.D. Faust and J.V. Hunter. John Wiley and Sons, New York, p. 625, 1967. Hering, J.G. and W. Stumm. Oxidative and Reductive Dissolution of Minerals. In Mineral-Water Interface Geochemistry Edited by M.F. Hochella, Jr. and A.F. White. Mineralogical Society of America, Washington, D.C., p. 427, 1990. Hsi, C.D. and D. Langmuir. Adsorption of Uranyl onto Ferric Oxyhydroxides: Application of the Surface Complexation Binding Site Models. Geochim. Cosmochim. Acta 49, pp. 1931-1941, 1985.

573 Kim, H.-T. and W.J. Frederick Jr. Evaluation of Pitzer Ion Internaction Parameters of Aqueous Electrolytes at 25~ Single Salt Parameters. J. Chem. EnQ. Data 33, pp. 177-184, 1988. Kluge, G., H. Saalfeld and W. Dannecker. Untersuchun,qen des LanQzeitverhaltens von M011verbrennun.qsschlacken beim Einsatz im Strassenbau. Unweltforschungsplan des Bundesministers des Innern, Forschungsbericht Nr. 103 03 006. Berlin, 1980. Krupka, K.M., R.L. Erikson, S.V. Mattigod, J.A. Schramke and C.E. Cowan. Thermochemical Data Used by the FASTCHEM Packa.qe. EPRI EA-5872, EPRI, Palo Alto, CA, 1988. Kummert, R. and W. Stumm. The Surface Complexation of Organic Acids on Hydrous u J. Colloid Interface Sci. 75, pp. 373-385, 1980. LaFlamme, B.D. and J.W. Murray. Solid/Solution Interaction: The Effect of Carbonate Alkalinity on Adsorbed Thorium. Geochim. Cosmochim. Acta 51, pp. 243-250, 1987. Leckie, J.O. Coordination Chemistry at the Solid/Solution Interface. In Metal Speciation: Theory, Analysis and Application Edited by J.R. Kramer and H.E. Allen. Lewis Publishing, Chelsea, MI, 41, 1988. Lindsay, W.J. Chemical Equilibria in Soils. J. Wiley and Sons, New York, 1979. Millero, F.J. and D.R. Schreiber. Use of Ion Pairing Model to Estimate Activity Coefficients of the Ionic Components of Natural Waters. Am. J. Sci. 282, pp. 15081540, 1982. Naumov, G.B., B.N. Ryzhenko and Khodakovsky. Handbook of Thermodynamic Data. US Geological Survey WRD-74-001. NTIS-PB-226 722/AS, Washington, D.C., 1974. Nordstrom, D.K. and J.L. Munoz. Geochemical Thermodynamics. Blackwell Scientific Publications, Palo Alto, CA, 1986. Nriagu, J.O. Lead Orthophosphates. IV. Formation and Stability in the Environment. Geochim. Cosmochim. Acta 38, pp. 887-898, 1974. Oberste-Padtberg, R. and K. Schweden. Zur Freisetzung von Wasserstoff aus M6rteln mit MVA-Reststoffen. Wasser Luft Boden 34, pp. 61-62, 1990. Pankow, J.F. Aquatic Chemistry Concepts. Lewis Publishers, Chelsea, MI,, 1991. Pankow, J.F. and J.J Morgan. Kinetics for the Aquatic Environment. I. Environ. Sci. Technol 15, pp. 1155-1164, 1981 a.

574 Pankow, J.F. and J.J. Morgan. Kinetics for the Aquatic Environment. II. Environ. Sci. Technol. 15, pp. 1306-1313, 1981b. Parker, V.B., D.D. Wagman and W.H. Evans. Selected Values of Chemical Thermodynamic Properties. Tables for the Alkaline Earth Elements (Elements 92 through 97 in the Standard Order of Arrangement). U.S. Nationa.I Bureau of Standards Technical Note 270-6, Gaithersburg, MD, 1971. Parks, G.A. Surface Energy and Adsorption at Mineral/Water Interfaces: an Introduction. In Mineral-Water Interface Geochemistry Edited by M.F. Hochella Jr. and A.F. White. Mineralogical Society of American, Washington, D.C., p. 133, 1990. Pitzer, K.S. Thermodynamics of Electrolytes. I. Theoretical Basis and General Equations. J. Phy..s. Chem. 77, pp. 268-277, 1973. Pitzer, K.S. Theory Ion Interaction Approach. In Activity Coefficients in Electrolyte Solutions. Edited by R. Pytkowicz. CRC Press, Boca Raton, FL, p. 157, 1979. Pitzer, K.S. Characteristics of Very Concentrated Aqueous Solutions. In Chemistry and Geochemistry of Solutions at Hi~..h Tempe.ratures and pressures. Edited by D.T. Rickard and F.E. Wickman. Pergamon, Oxford, p. 249, 1981. Pitzer, K.S. and L. Brewer. Thermodyn.amics, 2nd Edition, McGraw-Hill, New York, 1961. Pitzer, K.S. and J.J. Kim. Thermodynamics of Electrolytes. IV. Activity and Osmotic Coefficients for Mixed Electrolytes. J. Am. Chem. Soc_ 96, pp. 5701-5707, 1974. Pitzer, K.S. and G. Mayorga. Thermodynamics of Electrolytes. I1. Activity and Osmotic Coefficients for Strong Electrolytes with One or Both Ions Univalent. J.. Phys. Chem.. 77, pp. 2300-2308, 1973. Pourbaix, M. Atlas of Electrochemical Equilibria. Pergammon Press, Oxford, 1966. Pytkowicz, R.M. Equilibria, Nonequilibria, and Natural Waters, Vol. 1 and 2, John Wiley and Sons, New York, 1983. Rai, D. Inor.qanic and Organic Constituents in .Fossil Fuel Combustion Residues. Volume I A Critical Review. EPRI EA-5176, EPRI, Palo Alto, CA, 1987. Rai, D. and J.M. Zachara. Chemical Attenuation Rates, Coefficients and Constants in Leachate Mi,qration, Volume 1" A Critical Review.. EPRI EA-3356, EPRI, Palo Alto, CA, 1984.

575 Robie, R.A., B.S. Hemingway and J.R. Fisher. Thermodynamic Properties of Minerals and Related Substances at 298.1K and 1' Bar Pressure and at Hi.qher Temperatures. Geological Survey Bulletin No. 1452, U.S. Government Printing Office, Washington, D.C., 1978. Robie, R.A., B.S. Hemingway and J.R. Fisher. Thermodynamic Properties of Minerals and Related Substances at 298.15~ and 1 bar Pressure and at Higher Temperatures. Geolo.(]ical Survey Bulletin 1452. U.S. Government Printing Office, Washington, D.C., 1979. Rossotti, F. The Determination of Stability Constants.. McGraw-Hill Co., Inc., New York, 1981. Roy, W.R. and R.A. Griffin. Illinois Basin Coal Fly Ashes. 2. Equilibria Relationships and Qualitative Modelling of Ash-Water Reactions. Environ. Sci. Technol. 18, pp. 739742, 1984. Rubin, J. Transport of Reacting Solutes in Porous Media Relations Between Mathematical Nature of Problem Formulation and Chemical Nature of Reactions. Water Resources Res. 19, pp. 1231-1252, 1983. Scatchard, G. The Excess Free Energy and Related Properties of Solutions Containing Electrolytes. J. Am. Chem. Soc 90, pp. 3124-3127, 1968. Schindler, P.W. and W. Stumm. The Surface Chemistry of Oxides, Hydroxides and Oxide Minerals. In Aquatic Surface Chemistry. Edited by W. Stumm. John Wiley and Sons, New York, p. 83, 1987. Schnoor, J.L. Kinetics of Chemical Weathering: A Comparison of Laboratory and Field Weathering Rates. In Aquatic Chemical Kinetics" Reaction Rates of Processes in Natural Waters Edited by W. Stumm. John Wiley and Sons, New York, p. 475, 1990. Schnoor, J.L. and W. Stumm. The Role of Chemical Weathering in the Neutralization of Acidic Deposition. Schweiz Z. HYdrol. 48, pp. 171-193, 1986. Schott, J. and J.-C. Petit. New Evidence for the Mechanisms of Dissolution of Silicate Minerals. In Aquatic Surface Chemistry Edited by W. Stumm. John Wiley and Sons, New York, p. 293, 1987. Schott, J., R.A. Berner and E.L. Sj0berg. Mechanism of Pyroxene and Amphibole Weathering. I. Experimental Studies of Iron-Free Minerals. Geochmi. Cosmoch.im. Acta 45, pp. 2123-2135, 1981.

576 Schumm, R.H., D.D. Wagman, S.M. Bailey, W.H. Evans and V.B. Parker. Selected Values of Chemical Thermodynamic Properties. Tables for the Lanthanide (Rare Earth) Elements (Elements 62 through 76) in the Standard Order of Arrangement. U.S. National Bureau of Standards Technical Note 270-7. U.S. Government Printing Office, Washington, D.C., 1973. Schwertmann, U. and R.M. Taylor. Iron oxides. In Minerals in Soil Environments Edited by J.B. Dixon and S.B. Weed. Soil Science Society of America, Madison, WI, p. 145, 1977. Sigg, L. Surface Chemical Aspects of the Distribution and Fate of Metal Ions in Lakes. In Aquatic Surface Chemistry Edited by W. Stumm. John Wiley and Sons, New York, p. 319, 1987. Sigg, L. and W. Stumm. The Interactions of Anions and Weak Acids with the Hydrous Goethite (a-FeOOH) surface. Colloids Surf. 2, pp. 101-117, 1981. Sill~n, L.G. and A.E. Martell. Stability Constants of Metal-Ion Complexes. Supplement No. 1, Chemical Society, London, 1971. Smith, R.M. and A.E. Martell..Critical Stability Constants. Plenum Press, New York, 1976. Sposito, G. The Thermodynamics of Soil Solutions, Clarendon Press, Oxford, 1981. Sposito, G. Chemical Models of Inorganic Pollutants in Soils. CRC Crit. Rev. Environ. Control 15, pp. 1-24, 1984. Sposito, G..The Chemistry of Soils, Oxford University Press, N.Y., 1989. St~mpfli, D. Final Report: Cement and Bottom Ash Chemistry (CABAC). ERG Report. UNH, Durham, NH, 1992. St~mpfli, D., H. Belevi, R. Fontanive, and P. Baccini. Reactions of Bottom Ashes from .MSW Incinerators and Construction.Waste Samples with Water. EAWAG Project 3335, EAWAG, Dubendorf, Switzerland, 1990. Stumm, W. and G. Furrer. The Dissolution of Oxides and Aluminum Silicates; Examples of Surface Coordination-Controlled Kinetics. In Aquatic Surface Chemistry, Edited by W. Stumm. John Wiley and Sons, New York, p. 197, 1987. Stumm, W. and J.J. Morgan. Aqu.atic Chemistry.. John Wiley and Sons, New York, 1981.

577 Stumm, W. and E. Weiland. Dissolution of Oxide and Silicate Minerals: Rates Depend on Surface Speciation. In Aquatic Chemical KineticsLReaction Rates of Processes in. Natural Waters Edited by W. Stumm. John Wiley and Sons, New York, p. 367, 1990. van der Wegen, G. Orienterend Onderzoe.k. Naar O.orzaak Binding in een Monster AVISlakken. Rapportnumme, 91149, Intron, the Netherlands, 1991. Verink, E.D. Simplified Procedure for Constructing Pourbaix Diagrams. J. Educational Modules Materials Sci. EnQineer 1, pp. 535-560, 1979. Wagman, D.D., W.H. Evans, V.B. Parker, I. Halow, S.M. Bailey and R.H. Schumm. Selected Values of Chemical Thermodynamic Properties. Tables for the First ThirtyFour Elements in the Standard Order of Arrangement. _U.S. National Bureau of Standards Technical Note 270-3 U.S. Government Printing Office, Washington, D.C., 1968. Wagman, D.D., W.H. Evans, V.B. Parker, I. Halow, S.M. Bailey and R.H. Schumm Selected Values of Chemical Thermodynamic Properties. Tables for Elements 35 through 53 in the Standard Order of Arrangement. U.._S.National Bureau of Standards. Technical Note 270-4 U.S. Government Printing Office, Washington, D.C., 1969. Wagman, D.D., W.H. Evans, V.B. Parker, I. Halow, S.M. Bailey, R.Ho Schumm and K.L. Chumey. Selected Values of Chemical Thermodynamic Properties. Tables for Elements 54 through 61 in the Standard Order of Arrangement. U~S. National Bureau of. Standards Technical Note 270-5 U.S. Government Printing Office, Washington, D.C., 1971. Wagman, D.D., W.H. Evans, V.B. Parker, R.H. Schumm and R.L. Nuttall. Selected Values of Chemical Thermodynamic Properties. Compounds of Uranium, Protactinium, Thorium, Actinium, and the Alkali metals. U..S. N_ati0nal Bureau of Standards Technical. Note 270-8 U.S. Government Printing Office, Washington, D.C., 1981. Wagman, D.D., W.H. Evans, V.B. Parker, R.H. Schumm, I. Halow, S.M. Bailey, K.L. Churney and R.L. Nuttall. The NBS tables of Chemical Thermodynamic Properties. Selected Values for Inorganic and C1 and C2 Organic Substances in SI units. J. Phy. Chem. Ref. Data 11 (Supplement No. 2), pp. 1-392, 1982. Warren, C.J. and M.J. Dudas. Weathering Processes in Relation to Leachate Properties of Alkaline Fly Ash. J. Environ. Qual. 13, pp. 530-538, 1984. Warren, C.J. and M.J. Dudas. Formation of Secondary Minerals in Artificially Weathered Fly Ash. J. EnYiron. Qua!. 14, pp. 405-410, 1985. Warren, C.J. and M.J. Dudas. Mobilization and At..tenuati0n of Trac.e Elements in Artificially Weathered Fly .Ash. EPRI EA-4747, EPRI, Palo Alto, CA, 1986.

578 Wieland, E., B. Wehrli and W. Stumm. The Coordination Chemistry of Weathering: III a Generatlization on the Dissolution Rates of Minerals. Geochem. Cosmochim. Acta 52:1969-1981 Westall, J.C. and H. Hohl. A Comparison of Electrostatic Models for the Oxide/Solution Interface. Adv. Coll. Inter. Sci. 12, pp. 265-294, 1980. Whitfield, M. An Improved Specific Interaction Model for Seawater at 25~ Atmosphere Total Pressure. _Marine Chem. 3, pp. 197-213, 1975a.

and 1

Whitefield, M. The Extension of Chemical Models for Sea Water to Include Trace Components at 25~ and 1 Atmosphere Pressure. Geochim. Cosmochim. Acta 39, pp. 1545-1557, 1975b. Wollast, R. and L. Chou. Kinetic Study of the Dissolution of Albite with Continuous Flow-Through Fluidized Bed Reactor. In T.he Chemis..try of Weatherin.Q, Edited by J.l. Drever, NATO AI Series C 149, pp. 75-96, 1985. Zachara, J.M., D.C. Girvin, R.C. Schmidt and C.T. Resch. Chromate Adsorption on Amorphous Iron Oxyhydroxide in the Presence of Major Groundwater Ions. Environ. Sci. Technol. 21, pp. 589-594, 1987. Zachara, J.M. and G.P. Streile. Use of Batch and Cplumn..Methodolo.qies to Assess Utility Waste Leachin.q and Subsurface Chemical Attenuation. EPRI EN-7313, EPRI, Palo Alto, CA, 1991. Zevenbergen, C., J.P. Bradley, T. van der Wood, R.S. Brown, L.P. van Reeuwijk, and R.D. Schuiling. Weathering as a Process to Control the Release of Toxic Constituents from MSW Bottom Ash. In Geoconfine 93 Edited by M. Arnoud, M. Borres and B. C6me. A.A. Balkema, Rotterdam, p. 591, 1993.

579

CHAPTER 14- LEACHING TESTS 14.0 LEACHING TESTS Now that the concepts behind leaching phenomena have been introduced, discussing leaching tests is appropriate. Invariably, these tests are involved in the regulation of residues, as well as in the interpretation of leaching phenomena. Careful consideration should be given to the specific "tools" that are selected to characterise ash. Clearly, it is preferable to use a number of tools, rather than a single tool, for work in both science and regulation. At the end of this section, a unified theory of leaching is presented. This will move away from the strict use of concentration data and toward normalisation of leaching data to release, fractions leached and fluxes from residues. The rationale for using this approach to develop models and management scenarios will be discussed. Generalised and detailed reviews of leaching tests are found in Jackson et al. (1984), F,~llman (1990), Environment Canada (1990), Zachara and Streile (1991) and van der Sloot et al. (1991; 1993). The information from Environment Canada (1990) provides much of the basis for the following discussion.

14.1 PURPOSE OF LEACHING TESTS In general, a leaching test involves contacting a solid material with a leachant to determine which components in the solid will dissolve in the leachant and create a leaching solution or leachate. To investigate the various processes governing the extent and rate of leaching, endless variations can be introduced by changing test variables, such as leachant composition, method of contact, liquid-to-solid (L/S) ratio, contact time and system control (pH, pE (or Eh), temperature). Leaching tests have a wide range of objectives, the most common of which are presented in Table 14.1. Leaching tests are typically used to provide information about the constituent concentration or the constituent release from a waste material under reference test conditions, or under conditions that more closely approximate the actual disposal site. This information may subsequently be used in mathematical models to predict long term leaching.

14.1.1 Classification of Leaching Tests For the purposes of this discussion, leaching tests have been separated into two broad categories on the basis of whether or not the leachant is renewed: 1) extraction tests (no leachant renewal), and 2) dynamic tests (leachant renewal).

580 Table 14.1 .Leaching Test Objectives Objective

Description

Identification of leachable constituents

Determine which constituents of a waste are subject to dissolution upon contact with a liquid.

Classification of hazardous wastes

Compare wastes against performance criteria for classification of wastes as hazardous or nonhazardous.

Evaluation of process modifications

Determine if modifications to a wastegenerating process result in a less leachable waste.

Comparison of waste treatment methods

Determine whether a given waste treatment method/process results in superior containment of contaminants.

Quality control in waste treatment

Verify the efficiency of a treatment process using a simple pass/fail criterion.

Design of leachate treatment systems

Obtain a typical leachate to perform treatability experiments.

Field concentration estimates

Express leaching over time (e.g. to be used as a source term in groundwater modelling).

Parameter quantification for modelling

Quantify partition coefficients and kinetic parameters to be used in transport modelling.

Risk assessment

Estimate potential impact of waste disposal on the environment.

The concept of leachant renewal is based on modifying the leaching system to promote solution control of leaching rather than solid phase control.

Extraction Tests Extraction tests include all tests in which a specific quantity of leachant is contacted with a specific quantity of waste for a certain length of time, without leachant renewal. (This definition does not include analytical extractions or digestion procedures which are used to measure the total constituent concentration in an ash sample). The leachate is separated from the solid and analysed either at various times during the

581 test, or, as in most extraction tests, at the end of the test. The analysis of leachates generated at various times can help determine the kinetics of the leaching process or if equilibrium has been attained. The underlying assumption in this type of test is that an equilibrium condition is achieved by the end of the extraction test (i.e. the concentrations of solutes in the leachate become constant). In this no-flow system, an equilibrium condition occurs when there is no net transfer of components from the solid phase to the leaching solution, or vice versa. Sampling in an extraction test over time to derive kinetic information or to monitor the attainment of equilibrium is difficult since it must be done without modifying the residueleachant interactions, which are a function of factors such as the L/S ratio and gaseous exchanges. This can be accomplished in three ways: nondestructive sampling and analysis of parameters such as pH, conductivity or specific ions removing small volumes (aliquots) that are negligible when compared with the total volume preparing as many parallel extraction tests as data points required and performing destructive analyses.

Extraction tests can be further divided into four subcategories: agitated extraction tests non-agitated extraction tests sequential chemical extraction tests concentration buildup tests

Agitated Extraction Tests Agitated extraction tests (Figure 14.1) are performed to reach steady-state conditions as quickly as possible. They measure the chemical properties of a waste-leachant system, as opposed to rate-limiting mass transfer mechanisms. Agitation ensures a homogeneous mixture, promotes contact between the solid and the leachant and reduces boundary layer thicknesses. Sample particle size reduction is often performed to increase the surface area to volume ratio of the solid to enhance liquid/solid phase contact and to eliminate mass-transfer limitations. Generally, this reduces the duration of the test by reducing the time required to reach a pseudo-equilibrium condition in the leachate. This procedure may also have the effect of overestimating the short-term release of constituents. A steady-state leaching environment can also be attained in a column apparatus by recirculating the collected leachate back into the column.

582 Figure 14.1 Agitation Extraction Test

Crushed Solid Waste

Monolithic Solid Waste

o00 (:]DO ~

C]

OOO E]

Agitation

After Environment Canada, 1990

Non-agitated Extraction Tests A non-agitated extraction test is performed to study the physical mechanisms that are rate-limiting in leaching. The underlying assumption behind a non-agitated extraction test is that the physical integrity of the solid matrix and mass transfer constraints (both internally within the sample and externally in the boundary layer) affect the amount of contaminants that are leached during the test. Two types of non-agitated tests are illustrated in Figure 14.2. They can be performed on large particle-sized residue samples, concrete-type or monolithic samples. The disadvantage of running a non-agitated test is that a much longer contact period may be required to reach equilibrium conditions than is required in an agitated test. The advantage of this type of test is that rate-limiting mechanisms of leaching due to the physical integrity of the solid matrix are taken into account. These tests are presented in further detail in Chapter 20.

583 Figure 14.2 Static Leach Test

A) Static test with monolithic solid waste

A) Statictest with nonmonoUthic solid waste

After Environment Canada, 1990

Sequential Chemical Extraction Tests A sequential chemical extraction test is composed of a battery of non-agitated extraction tests (Figure 14.3). It involves performing sequential elutions of aliquots of a sample with different leachants (i.e. A, B, C, D and E in Figure 14.3), which are increasingly more aggressive in terms of chemical attack toward the residue (Figure 14.3a). One type of method assumes that each successive leachant also extracts the sum of contaminants extracted by all preceding leachants. The other type of method is conducted by subjecting the same aliquot of sample to each leachant (Figure 14.3b). The amount extracted in each elution is associated with a certain chemical form or mineral phase in the solid phase. The Sequential Chemical Extraction Procedure, originally compiled by Tessier et al. (1979), was adapted to sewage sludge incinerator ash by Fraser and Lure (1983), and then further modified for MSW incinerator ash (WTC, 1990). The test has been used in different studies (Wadge and Hutton, 1987) (Tessier Method); Environment Canada, 1993 (modified)), however, results by Khebohian and Bauer (1987) and discussion by Nirel and Morel (1990) (on the Tessier method) have shown that resorption and reprecipitation reactions can dramatically alter the mass fractions that are obtained in the different extractions. This limitation has been recognised and the latest studies using the modified method have basedmuch of their interpretation on the operationally defined extractions (e.g., peroxide extractable) rather than the implied chemical species (Environment Canada, 1993). Consequently, it appears that although the method is not appropriate for determining the chemical species, relating the operationally defined extractions to exposures under different leaching conditions (e.g., fraction available for leaching under acidic leaching conditions versus severe reducing conditions) is an appropriate set of interpretations.

584 Figure 14.3 Sequential Chemical Extraction Tests

Leachant a)

A

C

D

E

C

D

E

Wffh different waste samples

Leachant A b)

B

B

With the same waste sample and liquid/solid separation between elutions

After Environment Canada, 1990

Concentration Buildup Tests

In a concentration buildup test, an extraction is achieved at a very low cumulative L/S ratio. Aliquots of samples are successively contacted with the same leachant (Figure 14.4). The contact of leachate with fresh solid material can be considered as a model for an elemental volume of water flowing through a large body of residue and approaching saturation with respect to specific mineral phases. The purpose of this test is not to collect kinetic information, but to characterise a leachate saturated with soluble residue constituents. In some cases, this may simulate the actual pore water composition of a granular material in column leach tests or in outdoor disposal or utilisation scenarios.

Dynamic Tests

Dynamic tests include all tests in which the leachant is continuously or intermittently renewed to maintain a driving force for leaching that is solution-controlled. The intermittent tests may be conducted by alternating leaching periods with dry periods to study the effects of desiccation or unsaturated flow conditions. Dynamic tests provide information about the kinetics of solid phase dissolution and contaminant flux. Information is generated as a function of time, and attempts are often made to preserve the residue's physical integrity. These two factors lend this category of leaching tests to the investigation of more complex mechanisms of leaching.

585

Dynamic tests can be further divided into subcategories according to how the interface between the waste and the leachant is defined. Tests in which individual waste particles are used to define the interface are called serial batch tests. The tests in which a characteristic dimension of the waste, (such as the external geometric surface area or the geometric surface area perpendicular to flow) is used to define the interface include flow-around tests and flow-through or column tests.

Figure 14.4 Concentration Buildup Tests

1

2

N Discard

II

Agitation

After Environment Canada, 1990

Serial Batch Tests A serial batch test is conducted using a granular or crushed sample which is mixed with leachant at a given US ratio for a specified period of time (Figure 14.5). The leachate is then separated from the solids and replaced with fresh leachant until the desired number of leaching periods have been completed. The waste/leachant mixture is normally agitated to promote contact. Kinetic information regarding contaminant dissolution is obtained using the concentrations measured in the leachate from each of the leaching periods. Data from serial batch tests can be used to construct an extraction profile to infer the temporal release of leachable constituents. Flow-Around Tests In flow-around tests, a sample of residue is placed in the leaching vessel and the flow of fresh leachant around the residue provides the driving force to maintain leaching. The L/S ratio is modified to express the volume of leachant divided by the surface area

586 of the solid sample. Samples are usually monolithic, although non-monolithic or crushed residue may be used if it is confined in some manner. Agitation is generally not performed. Leachant flow is either continuous (Figure 14.6a), in which case it is sampled and analysed periodically, or it is intermittently renewed (Figure 14.6b). The latter method is generally simpler from an experimental point of view, but the renewal frequency must be sufficient to prevent a buildup of contaminants at the residue/leachant interface, which may inhibit further leaching by reducing the diffusional gradient.

Figure 14.5 Serial Batch Tests

m

m

m

AgitaUon After Environment Canada, 1990

Flow-Through Tests In a flow-through or column test, an open container is packed with a porous solid and leachant is passed through, either continuously or intermittently. The effluent is sampled periodically and analysed for the parameters of interest. The results are used to examine contaminant removal in which the primary transport mechanism is advection. There are two basic types of flow-through tests characterised primarily by the shape and size of the container. The first type is a column test which is performed using a small cylindrical container (Figure 14.7a). The second is a lysimeter test which is conducted in a large rectangular or cylindrical container (Figure 14.7b). In general, the size of the sample used in a flow-through test tends to be large to minimise the effects of sample heterogeneity and wall channelling effects. The depth of waste in either type of test varies according to the individual experiment.

587 Figure 14.6 Flow-Around Tests leachant

@

leachant

a) continuous leachate renewal

9

9

9

b) intermittent leachate renewal

After Environment Canada, 1990 Figure 14.7 Flow-Through Tests

leachant

leachant (downflow)

y_,

Y

leachant (upflow) I leachate

a) Columns After Environment Canada, 1990

b) Lysimeter

588 Columns may be operated either in an upflow or downflow mode, whereas lysimeters are always operated in a downflow mode. Flow through the solid depends upon its hydraulic conductivity, as well as the hydraulic gradient, and varies with the individual test. Mini-columns may be used to achieve a relatively rapid breakthrough of leached species. Since head losses may be large and a rapid breakthrough is desired, the leachant is usually delivered under pressure and at a constant flow rate. The advantages of minicolumns include: L/S ratios that are similar to those of real waste-leachant systems a known and easily varied average fluid velocity negligible axial dispersion or spreading of the solute a simple estimation of both equilibrium and kinetic coefficients automation permitting the rapid output of data. These tests are not applicable when large volumes of leachate are needed for a variety of analytical tests. Care should also be taken when conducting flow-through tests to avoid unnatural channelling of water and clogging by fine material or biological growth. In lysimeter tests, channelling cannot be avoided. It is a factor that occurs in the field, and its influence should be modelled in the laboratory, although quantifying it is difficult. Biodegradation of organics can also be a problem in columns, although in some cases experiments are intentionally set up to measure the effects of biological activity. Flowthrough tests can also be modified to examine other site-specific influences, such as vegetation on the surface of the container, or layered media, such as ash and geological material.

14.1.2 Leaching Test Variables There are several experimental variables which are common to all extraction and dynamic tests. These variables need to be considered when designing a leaching test for specific purposes.

Sample Preparation Depending on the nature of the waste and the test to be performed, the sample may require one of the following preparatory steps: 9 9 9 9 9 9 9 9

liquid/solid separation sub-sampling particle-size reduction surface washing compaction preservation curing aging

589 Liquid/solid separation may be performed on residues containing a free liquid phase. The leaching test is conducted only on the solid portion of the sample. The free liquid phase constitutes the initial leachate, which may be analysed separately to estimate the pore-water concentration or it can be included with the final leachate for analysis. Liquid/solid separation can be accomplished by various methods, including settling and decanting, centrifugation or pressure filtration through filter media of various types. Sub-sampling is generally required when several different tests or replicates are to be performed on the same sample. Waste samples should be thoroughly mixed before sub-sampling is performed. (See Chapter 6). Particle-size reduction is required for most extraction tests. The goal is to reduce the time required to reach steady-state conditions by increasing the contact surface area between the solid and the leachant. However, care should be taken to prevent the loss of volatile compounds in the solid if they are of interest. Particle-size reduction is usually carried out by grinding (e.g. mortar and pestle, centrifugal grinder or hammer mill). These issues are also discussed in more detail in Chapter 6 and 7. Surface washing may be performed prior to testing small monolithic samples in flowaround tests. The surface is washed to remove small detachable particles and readily soluble salts by quickly dipping the sample in an aqueous solution. Compaction or remolding is often required for flow-through tests. Reproducibility and field simulation considerations require that samples be compacted to a pre-specified density using methods such as vibration, proctor compaction or modified proctor compaction. Sample preservation is performed to avoid biological activity. This is a greater problem in tests of long duration, such as column tests. Various chemical treatments are available, such as the addition of sodium azide, however, none offer complete efficacy. Curing may be performed on samples that have been transformed into a solidified mass using various chemical additives, such as Portland cement. It allows the waste sample to gain physical and engineering properties, i.e. high unconfined compressive strength and low permeability, that are considered to be important in reducing leachability. Curing can be used to achieve a variety of chemical reactions within the waste, although this term usually refers to cement hydration reactions. Aging may be promoted on any type of waste sample to account for the physical, chemical and biological alterations that a waste might undergo in the field. Chapter 13 discusses classes of aging reactions that can occur in residues.

Leachant Composition The release of contaminants from a waste in any leaching test may be strongly influenced by the initial leachant composition, especially at high L/S ratios, or with the

590 use of an aggressive solution. Chemical properties of the leachant that influence contaminant mobilisation are indicated in Table 14.2. Examples of three types of commonly used leachants, i.e. water, site liquid and chemical solution, are identified in Table 14.3. Several advantages and disadvantages of these leachants are outlined in Table 14.4. Table 14.2 Important Factors in Leachant Composition Factor Release Mechanism Affected Dissolution/precipitation of metals, speciation of inorganic species Adsorption/desorption of solutes Oxidation/reduction of inorganic species Ionic exchange of metals, speciation chemistry and solubility products

pH

Eh, redox potential Ionic strength Chelating and complexing agents Buffering capacity After Environment Canada, 1990

Metal solubility All above properties

Table 14.3 Commonly Used Leachants Type of Leachant Water

Common Uses

Nonaggressive, baseline medium without buffering capacity Site liquid (real or Simulates site-specific synthetic) leaching conditions Chemical solution Examines metal speciation and organic compound binding After Environment Canada, 1990

Examples Distilled, deionised and tap water

Rainwater, groundwater, surface water, landfill leachant, seawater Strong chemical solution (acidic, basic, reducing, oxidising, complexing, solvent,etc.)

591 Table 14.4 Advantages.and D isadvantacjes of Commonly Used Leachants Leachant

Advantages

Disadvantages

Pure water

Reliable, simple standard

Lack of background composition may result in dissolution of common ions

Site liquid

Best field case model

Requires characterisation (to obtain leaching results by subtraction)

Several synthetic liquids available

Results not comparable with other leaching studies Labour intensive (sampling and preservation)

Chemical solution Allows for the study of waste chemistry After Environment Canada, 1990

Aggressive, difficult to relate data to field conditions

Method of Contact Since a leaching test is primarily a system to study the transfer of contaminants from a residue to a liquid, it is important to consider the aspects of the test conditions that promote mass transfer, such as agitation, and to consider the effect of mass exchange with other components of the system, primarily the leaching vessel and the atmosphere.

Agitation of the leachant-solid slurry generally hastens reaching equilibrium conditions by maintaining maximum contaminant concentration gradients at the leachant-solid particle interface. Different methods can be used to agitate the waste, including shaking (wrist action or reciprocation) stirring (magnetic or paddle) tumbling gas bubbling. In static or non-agitated tests, the leachant-solid interface is usually the geometrical surface area of the solid form. There is usually no provision for mixing because diffusion of leached constituents within the leachate is assumed to be much faster than the rate of release by mechanisms such as dissolution from the surface or diffusion from within ash particles. Ensuring that the leachate is well mixed before sampling is important, however.

592 It may be important to identify and quantify exchanges of chemical species other than between the solid and the leachant. Exchanges between the leachant and the leaching vessel are always undesirable, whereas exchanges with the atmosphere depend in large part upon the objectives of the test, such as leaching with carbonic acid. To minimise exchanges with the leaching vessel, glass or stainless steel should be used for organic contaminants and plastic for inorganic contaminants. If the cost is not prohibitive, polytetrafluoroethylene is considered to be acceptable for both. For the purpose of verifying the mass of constituents adsorbed to the container wall, the emptied leaching vessel can be extracted with a strong solvent. The test system may be either open or closed to the atmosphere. The choice depends on the specific leaching problem being examined. For example, a closed system provides a better simulation of the saturated groundwater environment, whereas an open system models problems like a storage pile and unsaturated disposal environments more accurately. An open system facilitates sampling, leachant renewal and periodic or continuous adjustment of the pH or redox potential. However, a system that is open to the atmosphere allows for the loss of volatile compounds, including water and organics, and the introduction of CO2 and 02 from the air. Losses due to evaporation may have to be accounted for in an open system. Although volatile organics are generally not a concern with incinerator ash, there are several apparatus configurations that will prevent volatile contaminants from escaping. If there is no headspace in the leaching vessel, volatiles will remain in either the solid phase or the leachate. If there is a headspace, volatiles will be partitioned in the gas phase. Analysis of the headspace allows for an evaluation of this loss. Even for experiments carried out in closed containers and under controlled conditions, penetration of gases through plastic container walls can have a significant effect, especially over long durations. This is seen in reaction vessels kept at a low redox potential when oxygen diffuses into the vessel.

Liquid-to-Solid Ratio The L/S ratio is the ratio of the amount of leachant in contact with the residue to the amount of waste being leached. Although this definition appears straightforward at first glance, it can become confusing because of the many ways in which the two variables in the ratio have been defined. The L/S ratio has been expressed as: volume of leachant/mass of solid mass of leachant/mass of solid and volume of leachant/surface area of solid (for monolithic material).

593 Furthermore, when using the first two expressions, the mass of solid being leached can be calculated on a wet weight or a dry weight basis. Another problem arises because of the various ways that the volume or mass of leachant can be calculated, depending on whether or not the liquid phase of the solid is included in the total leachant volume. The preferred way to report L/S is the mass of leachant to the dry mass of solid. Figure 14.8 illustrates how these various ways of defining the amounts of waste and leachant can give different L/S ratios for the same system. The three fractions shown in Figure 14.8 include the amount of leachant added, the liquid phase associated with the solid, and the solid phase.

Figure 14.8 Liquid and Solid Fractions of the Waste Leachant System ,,,

A

Added Leachant

B Liquid Phase of Waste C

Solid Phase of Waste

After Environment Canada, 1990

If the residue is dry, then the L/S ratio is simply A/C. If the residue is wet, there are three ways to define the L/S ratio: 1) the residue is the sum of the liquid and solid phases, i.e. L/S = N(B+C). 2) the leachant is the sum of the amount of leachant added plus the liquid phase associated with the solid, i.e. L/S = (A+B)/C 3) the liquid phase associated with the solid is excluded from the calculations, and residue is the solid phase only, i.e. L/S = A/C.

594 Leachate concentrations of highly soluble species (e.g. sodium, potassium) are generally inversely proportional to the L/S ratio of all of the species which have been removed from the solid. However, if the release of a species is limited by solubility, the final concentration is independent of the L/S ratio and simply equals the maximum solubility concentration. In general, the leachate concentration will be controlled by a number of competing factors, namely, the amount of contaminant available, solubility and kinetically controlled chemical reactions. Thus, the relationship between the L/S ratio and concentration is complex, and different for each species of interest. Selection of an appropriate US ratio depends on the objectives of the leaching test, the solubility of species of interest and analytical constraints. The ratio should be low enough to avoid dilution of contaminants to less than analytical detection limits. However, the ratio also must be high enough to prevent solubility constraints from limiting the amount of contaminants that can be leached from the waste. The selected ratio should be somewhere between these two limitations. Practical values for the L/S ratio range from 0.1 to 100:1. To place these values into perspective, most landfilled residues are exposed to L/S values of less than 3:1 during the operational life (10 to 20 years) of a disposal facility. After closure, the type and integrity of the cap will influence further increases in the L/S.

Contact Time The total amount of time that a leachant is in contact with a solid sample before the attainment of equilibrium will influence the amount of contaminant released. In extraction tests, the contact time is equivalent to the duration of the test, whereas in dynamic tests, it is a function of the flow rate, or the number of elutions, in addition to the test duration. The contact time for extraction tests should allow equilibrium conditions to be reached for the contaminants of interest. This is generally in the order of hours to days for samples that have undergone particle-size reduction. For concrete-based or monolithic samples, it can be in the order of weeks to months. The contact time for dynamic tests should be sufficient to allow for observation of the processes of interest. Diffusion processes may be quantified within a few weeks, although several months may be required to study slow chemical reactions.

Temperature Temperature affects the results of extraction and dynamic tests. Both the van't Hoff relationship, which applies to thermodynamic equilibrium constants and solubility products, and the Arrhenius relationship, which applies to kinetic processes such as adsorption and diffusion, indicate that properties or mechanisms relevant to leaching vary exponentially with temperature.

595 For convenience, most leaching tests are performed at room temperature. Higher temperatures may be used to accelerate the rate of leaching (although this may also change the properties of the waste) or to simulate the effects of biological activity in a landfill or the self-heating from exothermic reactions.

Leachate Separation Leachates are commonly separated from agitated non-monolithic wastes by filtration using a 0.45 pm membrane filter (a convention used to define soluble species). However, very small colloid particles can pass through a 0.45 pm filter. A smaller pore size filter (0.2 pm) should be used if these particles are to be removed. The use of the smaller filter size should be reported with the data. Glass fibre filters are chosen when hydrophobic, low solubility organic molecules are expected in the leachate since they may have a high affinity for filters composed of an organic polymer. Membrane filters, such as cellulose acetate, should be used for metal species in place of glass. The same care used to select a leaching vessel should be applied when selecting the filter material. Filtering the leachate from non-agitated monolithic samples may not be necessary if the method of contact generates only dissolved species. This should be verified before sampling.

14.1.3 Compilation of Leaching Tests The leaching tests presented in Environment Canada (1990), Fallman (1990), and van der Sloot et al. (1991, 1993) serve as the basis for the compilation of various leaching tests presented here. The reader can refer to these references for precise details of each method. Table 14.5 summarises the various agitated batch extraction tests that are used for regulatory purposes or for research into leaching characteristics of waste. All the methods specify the type of leaching vessel to be used, the type of sample preparation that is required, the amount of sample that is needed, the type of leachant to be employed, the L/S ratio that is used, the type of agitation that is required and the duration of the test. Most methods also specify the type of filtration that is to be employed to allow for quantification of total dissolved constituents in the leachate. Table 14.6 specifies two non-agitated extraction tests that are commonly used to examine sequential dissolution of mineral phases in a solid or the fundamental dissolution and effective diffusion parameters of a solid dissolving under static conditions.

Table 14.5 Agitation Leach Tests Test Name and Proponent

Status of Leaching Development Vessel

Sample Preparation

Sample Mass

Leachant

-EP f o x U.S. EPA Method 1310

Standard regulatory method (1980)

Unspecified

-LEP MOE (Ontario)

Standard regulatory method (1985)

-TCLP U.S. EPA Method 1311

US Ratio

Non-monolithic waste; phase separation Monolithic waste; particle-size reduction

100 g

Deionised water 0.5 N acetic acid (max. 2.0 meq H+lg solid)

20:l

Wide mouth, 1250 mL cylindrical bottle

Phase separation by 0.45 pm membrane filter

50 g of d?, sol~ds

Distilled water Acetic acid (2.0 meq H+lg dry solids)

20.1

End over end (10 rPm)

24 hours

0.45 pm filtration

Standard regulatory method (1986)

Any material compatible with waste, zero head-space extractor (ZHE) for volatiles

Cuttinglcrushing and grinding Solidlliquid phase separation No structural integrity

100 g (25 g for ZHE)

Buffered acetic acid 1) pH = 4.93 2) pH = 2.88

20:l

End over end (30 rpm)

18 hours

0.6 to 0.8 pm borosilicate glass fibre filter combines liquid phase with extract

-Q.R.S.Q. MOE (Quebec)

Standard regulatory method (1987)

>1 L bottle

No phase separation 100 g dry Inorganics: buffered Grinding solids acetic acid (0.82 No structural integrity 50 g for meq H+lg dry volatiles solids) Organics: distilled water

10:l

End over end (10 to 20 rPm)

24 hours

30 min decantation, 0.45 pm filtration

-WET California

Standard regulatory method (1985)

Polyethylene or glass container

Milling, 0.45 pm filtration

50 g

0.2 M sodium citrate at pH 5.0

10:l

Table shaker Rotary Extractor

48 hours

Centrifugation 0.45 pm filtration

-X31-210 French Leach Test AFNOR (France)

Proposed standard for waste (Dec 1992)

Straight wall, 2 L bottle

Remove free liquid Reduce particle size to