Water Treatment Plant Residuals Field Guide

Transcription

1 Water Treatment Plant Residuals Field Guide i

2 ii

3 Water Treatment Plant Residuals Field Guide Nicholas G. Pizzi

4 Copyright 2010 American Water Works Association All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information or retrieval system, except in the form of brief excerpts or quotations for review purposes, without the written permission of the publisher. Disclaimer This book is provided for informational purposes only, with the understanding that the publisher, editors, and authors are not thereby engaged in rendering engineering or other professional services. The authors, editors, and publisher make no claim as to the accuracy of the book s contents, or their applicability to any particular circumstance. The editors, authors, and publisher accept no liability to any person for the information or advice provided in this book or for loss or damages incurred by any person as a result of reliance on its contents. The reader is urged to consult with an appropriate licensed professional before taking any action or making any interpretation that is within the realm of a licensed professional practice. AWWA Publications Manager: Gay Porter DeNileon Project Manager: Mary Kay Kozyra Cover Art/Production Editors: Cheryl Armstrong Library of Congress Cataloging-in-Publication Data ISBN ISBN iv

5 Contents Contents... v Acknowledgments... vii Introduction... 1 Regulations and Goals Filter Backwash Recycle Rule 1 National Pollutant Discharge Elimination System 2 Operations... 5 Theoretical Considerations for Operators 5 Types of Waste 6 Waste Handling 11 Nonmechanical and Mechanical Dewatering Processes Polymer Screening 23 Nonmechanical dewatering: sand beds, lagoons, and solar/evaporation ponds 25 Mechanical dewatering: filter presses, centrifuges, belt presses, and vacuum systems 29 Operational Techniques 36 v

6 Design Theory Operational Use of Design Calculations 42 Operational Goal Setting 45 Glossary References Appendix vi

7 Acknowledgments The author thanks David Cornwell, Ph.D., PE, of EE&T Inc., and Timothy Wolfe, Ph.D., PE, of MWH Americas Inc., for their technical advice. The author also thanks the Cleveland Division of Water for the use of some of the photos found herein. vii

8

9 Introduction AWWA s pocket field guides provide water treatment plant operators with the basic information they need to perform their jobs. The guides, which are designed to be carried in the shirt pocket, are divided into general sections and include a glossary and reference list. This field guide is based on regulatory, theoretical, operational, inspection, and maintenance issues related to treatment plant residuals processes. It is suited for operators who use conventional coagulation of water in a pretreatment process or who soften water with lime and/or soda ash or caustic. Although some treatment plants use membranes in various schemes or ion-exchange processes that produce brines, this guide focuses on conventional and direct filtration plants, as well as precipitative softening plants. There are also watershed management techniques that aim to minimize the solids loading at the treatment plant site; however, this guide does not address those techniques. Historically, handling and treating waste streams in water treatment plants was a stand-alone management issue. However, due to rising design and disposal costs and the potential for harmful effects on the treatment process, the handling of treatment plants wastes (residuals) has become so important that it is now considered a unit process with specific design and operational parameters associated 1

10 with it. This guide will help staff operate the process within those parameters.