Diatomaceous Earth Filtration for Safe Drinking Water

Transcription

1 Diatomaceous Earth Filtration for Safe Drinking Water GEORGE P. FULTON American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia

2 Abstract: First adopted by the U.S. Army during World War II, diatomaceous earth (DE) filtration is a viable water treatment method that produces drinking water from low-turbidity sources. This book reviews the range of DE filter equipment, as well as the process performance features of filtration and supplemental treatment units. Performance is evaluated according to the standards set by current and anticipated regulations governing the quality of drinking water. Comparisons are made with other, more traditional methods of water treatment to highlight the particular advantages of DE filtration. Details of comprehensive procedures are presented for the engineer, starting with collection and devleopment of the background data used in preliminary studies and leading to the preparation of final design documents for construction. Site considerations are covered, as are operation and maintenance manuals, including detailed lists of features to consider in troubleshooting DE filter operation faults. Library of Congress Cataloging-in-Publication Data Fulton, George P. Diatomaceous earth filtration for safe drinking water / George P. Fulton, p. cm. Includes bibliographical references and index. ISBN Water Purification Diatomaceous earth filtration. 2. Drinking water Purification. I. Title. TD466.F '64 dc Any statements expressed in this material are those of the author and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process, or service constitutes or implies an endorsement, recommendation, or warranty thereof by ASCE. This material is for general information only and does not represent a standard of ASCE, nor is it intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. ASCE makes no representation or warranty of any kind, whether express or implied, concerning the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed in this publication, and assumes no liability therefore. This information should not be used without first securing competent advice with respect to its suitability for any general or specific application. Anyone utilizing this information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. Photocopies: Authorization to photocopy material for internal or personal use under circumstances not falling within the fair use provisions of the Copyright Act is granted by ASCE to libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $8.00 per chapter plus $.50 per page is paid directly to CCC, 222 Rosewood Drive, Danvers, MA The identification for ASCE Books is /00/$ $.50 per page. Requests for special permission or bulk copying should be addressed to Permissions & Copyright Department, ASCE. Copyright 2000 by the American Society of Civil Engineers. All Rights Reserved. Library of Congress Catalog Card No: ISBN Manufactured in the United States of America

3 Contents Preface Acknowledgments 1 Introduction 1 DlATOMACEOUS EARTH MEDIA / 2 APPLICATION AND HISTORICAL BACKGROUND / 3 POROUS MEDIA FILTERS / 6 THE DIATOMACEOUS EARTH FILTER AND PERTINENT REGULATIONS /13 MULTIPLE DESIGN/OPERATION OPTIONS / 23 PRELIMINARY RESEARCH / 27 2 Diatomaceous Earth Filter Types and Options 29 GENERAL / 29 INITIAL FILTER DESIGNS / 31 HYDRAULIC MODES OF OPERATION / 35 CONTAINMENTS / 39 FILTER LEAF ASSEMBLY / 41 BAFFLED INLETS / 48 OUTLET MANIFOLDS / 50 SLUICING SPRAYS / 50 PRESSURE FILTER OPTIONS / 51 VACUUM FILTER OPTIONS / 56 3 Principal Performance Features 59 PRINCIPAL PARTICULATE FEATURES / 59 HEAD Loss AND BODY FEED / 62 ENHANCED SOLIDS REMOVAL / 67 BREAKTHROUGH POTENTIAL / 71 COLOR REMOVAL / 73 IRON AND MANGANESE / 74 DISINFECTION BYPRODUCTS / 80 v ix iii

4 IV DIATOMACEOUS EARTH FILTRATION FOR SAFE DRINKING WATER 4 Filter and Ancillary Systems 85 BASIC PRESSURE FILTER SYSTEM / 86 BASIC VACUUM FILTER SYSTEM / 90 MULTIPLE FILTER ARRANGEMENTS / 94 DELIVERY AND STORAGE OF DRY DIATOMACEOUS EARTH / 97 DIATOMACEOUS EARTH SLURRY STORAGE AND TRANSFER /102 DIATOMACEOUS EARTH RECOVERY AND RECYCLE /106 WASTE DISPOSAL /108 5 PilotTesting 113 SIMULATION /113 PROCESS VARIABLES /115 PILOT PROGRAM DESIGN /121 BUCHNER FUNNEL TEST /125 FUNDAMENTAL PILOT FILTER TESTS /131 SQUARE FOOT PRESSURE FILTER /136 PILOT VACUUM FILTER /146 SUPPLEMENTARY TREATMENT /147 TEST DATA /147 PRINCIPAL PROCEDURE CONSIDERATIONS /152 PILOT OPERATION TROUBLESHOOTING /156 6 Equipment and Materials of Construction: Principal Safety and Design Features 161 INFLUENCING FACTORS /161 SYSTEM HYDRAULICS /163 WATER SUPPLY PUMPS /164 SLURRY HANDLING /168 INSTRUMENTATION AND CONTROLS /173 7 Design and Operation 177 POTENTIAL APPLICATIONS /177 DESIGN PROCEDURES /180 PRELIMINARY ENGINEERING /187 CONTRACT DOCUMENTS: CONSTRUCTION / 206 START-UP/TROUBLESHOOTING OPERATION / 207 References 210 Index 211

5 Preface Diatomaceous earth (DE) filtration has been an effective method for treatment of low turbidity drinking water supplies since World War II. At that time, it was adopted for use for the U.S. Armed Forces. The Army developed the industrial filter for drinking water application because a lightweight, easily transportable filter unit, capable of removing Entamoeba histolytica cysts was required. In subsequent tests in the 1980s and after, DE filtration was shown to be the superior alternative for removing Giardia and Cryptosporidium cysts in the treatment of drinking water. Despite effective performance, DE filters have had limited use in the treatment of public drinking water supplies in the ensuing period. The several options of rapid sand filter trains using coagulation/flocculation for source water solids conditioning have dominated drinking water treatment since the turn of the century. It is interesting to observe that there has been little change in the basic form of rapid sand filter systems in over a century of use. Certain mechanical features, new materials of construction, and polyelectrolytes to assist coagulation/flocculation have been developed to somewhat change the look of these treatment trains and improve treatment performance. Alum is still the predominant coagulant used to condition solids for removal. In addition to sand, the granular media may also include ground anthracite, a combination of sand and anthracite, and granulated activated carbon. The academic community has also been reluctant to change sights in the investigation of different methods of drinking water treatment. The elusiveness of the "workings" of the coagulation/flocculation phenomena have provided "meat" for thousands of advanced degree research projects in the past. These investigations still continue and will, no doubt, go on indefinitely in the future in pursuit of the absolute model of the phenomena. On the other hand, diatomaceous earth filtration is a simple, physical V

6 VI DIATOMACEOUS EARTH FILTRATION FOR SAFE DRINKING WATER separation process for the removal of suspended matter from a flow of drinking water. Robert Bauman produced the definitive work on the operation of DE filters at the Iowa University in the 1960s. There is little left for academic investigation other than DE filtration performance treating different sources of water certainly not very promising thesis material compared to the pursuit of the elusive rapid sand filter performance model. As further testament of its efficacy, DE filtration has for many years been the mainstay of the beverage industry in the production of wine and beer. Beverage standards are perhaps more stringent than those for drinking water. This industry use has been responsible for the development of new, improved filtration equipment that may also be used in the treatment of drinking water. The reader will notice that there are few references at the end of each chapter. This is because very little investigation had been made of DE filtration until the mid-1970s. At that time, the City of New York embarked on a major research program for its Croton watershed supply. DE filtration was a major consideration in these investigations and considerable research data was developed in three successive research programs. The principal performance data used in this text was developed in two of the programs, included in the following reports: Metcalf & Eddy, Inc.: Hazen and Sawyer, 1994 Final Report on Development of Design Criteria for the New Croton Water Treatment Plant at Jerome Park Reservoir, Borough of the Bronx, City of New York, February. Metcalf & Eddy, Inc.: Hazen and Sawyer, 1999 Final Report on Additional Pilot Studies for the Croton Water Treatment Plant, January. Little historical background is available about DE filtration from its original use in industry to its present day applications for drinking water and beverage production. This information was pieced together by the author from industrial brochures and interviews with knowledgeable people in the various areas of DE use. The principal purpose of this text is two-fold: 1. To acquaint those who are unfamiliar with DE filtration or those who have misconceptions about the process with both the advantages and

7 PREFACE Vll limitations in using this relatively simple method of treatment in applicable drinking water situations. 2. To provide guidelines for the professional in the development of designs of complete DE facilities and in subsequent start-up and plant operation to produce safe drinking water. Background theory and practical performance data are provided to assist in the evaluation of DE filtration for different drinking water applications for meaningful comparisons with alternative treatment. Information is provided to permit design of complete DE facilities from material delivery and handling through DE filtration systems to ultimate waste disposal.

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9 Acknowledgments In todays world of detailed and complex technology, a text of this kind does not result from the endeavors of a single individual. The author is grateful to the City of New York for sponsoring the intensive, comprehensive research program for treatment of the Croton water supply from which a considerable portion of the information used in this book was obtained. In particular, the author recognizes the contributions to that project of members of the Hazen and Sawyer staff: Raymond Mclndoe, supervisor of the initial demonstration project: Michael Broder, facilities designer for the demonstration project and subsequent pilot research; and David Rokjer, who dedicated a good portion of a decade to accumulating data on diatomaceous earth filtration performance. The author also acknowledges with grateful thanks Anita Schleider, for her time and patience devoted to the preparation of the manuscript, as well as Gail Yap and Helen Yoon, whose computer graphics talents are demonstrated by the illustrations included herein. The author also wishes to thank Michael Elliott of Stearns and Wheler for his peer review of the text. He has served as Chairman of the Precoat Filtration Subcommittee of the AWWA Coagulation and Filtration Committee. In addition to the technical comments, the author is grateful for his advice in moderating the sometimes too ebullient writing style. The author also thanks both the Celite Corp. and Eagle-Picher Minerals, Inc. for providing background information on the source, mining, manufacturing, delivery, handling, and physical property features of diatomaceous earth media. These data were helpful, not only in the preparation of the text, but also in the design of many of the Chapter 4 graphics. IX