F u n d N Fundamentals and a m itrification is a microbiological process by which reduced nitrogen compounds e n (primarily ammonia) are sequentially oxidized to nitrite and nitrate. Nitrification can t a be problematic in potable water systems that use chloramines for residual (secondary) ls Control of Nitrification a disinfection. AWWA Manual M56, Fundamentals and Control of Nitrification in n d Chloraminated Drinking Water Distribution Systems summarizes existing knowledge C in Chloraminated Drinking o and provides updated information on the current practices of water suppliers and issues n t r related to nitrification; provides water utilities with the latest information on nitrification o l in water distribution systems; provides information to help utilities maintain a o Water Distribution Systems f chloramine residual in tap water; and helps utilities effectively mitigate nitrification N i t episodes that may occur in their systems. ri f i c a t i o n M M 56 Manual of Water Supply practiceS 5 6 First Edition AWWA is the authoritative resource for knowledge, information and advocacy to improve the quality and Advocacy supply of water in North America and beyond. AWWA is the largest organization of water professionals in Communications the world. AWWA advances public health, safety and welfare by uniting the efforts of the full spectrum of Conferences the entire water community. Through our collective strength we become better stewards of water for the Education and Training greatest good of the people and the environment. Science and Technology Sections POS-1E-30056-6/09-LS The Authoritative Resource on Safe Water ® 9781583214190-Perfect.indd 1 5/26/2009 4:33:00 PM Fundamentals and Control of Nitrification in Chloraminated Drinking Water Distribution Systems AWWA MANUAL M56 First Edition MANUAL OF WATER SUPPLY PRACTICES—M56, First Edition Fundamentals and Control of Nitrification in Chloraminated Drinking Water Distribution Systems Copyright © 2006 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 The authors, contributors, editors, and publisher do not assume responsibility for the validity of the content or any consequences of its use. In no event will AWWA be liable for direct, indirect, special, incidential, or consequential damages arising out of the use of information presented in this book. In particular, AWWA will not be responsible for any costs, including, but not limited to, those incurred as a result of lost revenue. In no event shall AWWA’s liability exceed the amount paid for the purchase of this book. Project Manager/Senior Technical Editor: Mary Kay Kozyra Manuals Coordinator: Beth Behner Produced by Glacier Publishing Services, Inc. Library of Congress Cataloging-in-Publication Data Fundamentals and control of nitrification in chloraminated drinking water distribution systems.--1st ed. p. cm. -- (AWWA manual ; M56) Includes bibliographical references and index. ISBN 1-58321-419-4 1. Water--Purification--Nitrogen removal. 2. Water--Purification--Chloramination. 3. Nitrification--Prevention. 4. Dentrification. 5. Drinking water--Contamination-- Prevention. 6. Water--Distribution--Safety measures. I. American Water Works Association. II. Series. TD427.N5F86 2006 628.1'662--dc22 2006042800 Printed in the United States of America American Water Works Association 6666 West Quincy Avenue Denver, CO 80235-3098 ISBN 1-58321-419-4 Contents List of Figures, vii List of Tables, xi Preface, xiii Acknowledgments, xv Chapter 1 Introduction to Nitrification in Drinking Water and Its Impact on Regulatory Compliance . . . . . . . . . . 1 Introduction, 1 Distribution System Disinfection Practices, 3 History of Chloramination in the United States, 4 Nitrification Basics, 5 Nitrification and Regulatory Compliance, 8 Conclusions, 11 References, 13 Chapter 2 Nitrification in Water and Wastewater Treatment . . . . 15 Introduction, 15 Nitrification in Drinking Water Treatment Processes and Impact on the Distribution System, 15 Nitrification in Wastewater Treatment Processes, 19 Comparisons Between Nitrification in Water and Wastewater, 21 Conclusions, 22 References, 23 Chapter 3 Nitrification in Drinking Water Distribution Systems . . 25 Introduction, 25 Nitrification in Drinking Water Distribution System, 25 Nitrification in Pipelines and Effects of Biofilms, 31 Nitrification in Water Storage Facilities, 34 Conclusions, 39 References, 39 Chapter 4 Overview of Causes and Control of Nitrification in Water Distribution Systems . . . . . . . . . . . . . . . 43 Introduction, 43 Conditions Promoting and Limiting the Growth of Nitrifying Bacteria in Drinking Water Distribution Systems, 43 Chloramine Demand and Decay as a Major Cause of Nitrification, 52 Treatment Options to Manage Chloramine Demand and Decay, 54 Example of an Impact of Chloramine Demand/Decay on Nitrification, 62 Conclusions, 65 References, 66 iii Chapter 5 Microbiology and Isolation of Nitrifying Bacteria . . . . 69 Introduction, 69 Taxonomy and Morphology of Nitrifying Bacteria, 69 Isolation and Enumeration of Nitrifying Bacteria, 89 Conclusions, 93 References, 95 Chapter 6 Growth and Inactivation of Nitrifying Bacteria . . . . . 99 Introduction, 99 Optimum Growth Conditions for Ammonia- and Nitrite-Oxidizing Bacteria, 99 Growth of Denitrifying Bacteria, 113 Inactivation by Disinfectants, 115 Conclusions, 123 References, 124 Chapter 7 Monitoring for Nitrification Prevention and Control . . . 129 Introduction, 129 Monitoring Program Goals and Parameters, 129 Relative Usefulness of Monitoring Parameters, 131 Description of Monitoring Parameters, 131 Monitoring Frequency, 147 Conclusions, 148 References, 149 Chapter 8 Operational and Treatment Practices to Prevent Nitrification . . . . . . . . . . . . . . . . . . 151 Introduction, 151 Ammonia Control, 154 Chloramine Residual, 165 Storage Facility Operation, 168 Distribution System Operation, 175 Assessment of Preventative Operational Measures, 184 Conclusions, 184 References, 185 Chapter 9 Assessment and Operational Responses to Nitrification Episodes . . . . . . . . . . . . . . . . . 189 Introduction, 189 Nitrification Assessment, 189 Developing a Nitrification Response Plan, 196 Responses to Distribution System Nitrification Episodes, 200 Responses to Nitrification Episodes in Distribution System Storage Facilities, 212 Conclusions, 218 References, 218 iv Chapter 10 Capital Improvements for Nitrification Prevention . . . 221 Introduction, 221 Improvements to Reservoir Mixing and Decreasing of Water Age, 221 Modifications to Piping and Pressure Zones, 235 Boosting Combined Chlorine Residual in Chloraminated Distribution Systems, 236 Conclusions, 246 References, 246 Additional Reading, 249 Abbreviations and Acronyms, 251 Units of Measure With Metric Conversions, 255 Index, 259 List of AWWA Manuals, 269 v This page intentionally blank. Figures 1-1 Main biological processes involving nitrogen transformation, 6 1-2 Ammonia and nitrite levels at one utility, 12 1-3 Comparison between plant effluent and distribution system concentrations of nitrite, 12 2-1 Typical Nitrosomonas specific growth rate versus ammonia concentration at 20°C, 20 3-1 Nitrification episode in a South Australian distribution system, 33 3-2 Seasonal relationship between temperature, AOB, and nitrite in a California reservoir, 36 4-1 Effect of pH on monochloramine decay as a function of pH at 25°C, 53 4-2 Evidence of different mechanisms of ammonia release from chloramine decay in conventionally coagulated water at pH 7.5, 54 4-3 Impact of coagulation and ozonation on chloramine demand, 55 4-4 Effect of TOC removal by GAC adsorption on chloramine demand, 56 4-5 Effect of inert and biologically active filtration on chloramine demand, 59 4-6 Effect of membrane filtration on chloramine demand, 60 4-7 Effect of postfilter chlorine dioxide dose on chloramine demand, 61 4-8 Characteristics of chloramine demand/decay in a California plant’s effluent waters, 63 4-9 Free ammonia release from chloramine demand/decay in a California plant’s effluent waters, 64 4-10 Total chlorine to total ammonia-N weight ratio resulting from chloramine demand/decay reactions in a California plant’s effluent waters, 64 5-1 Nitrifying bacterial zoogloea, 74 5-2 Nitrifying bacterial cyst, 75 5-3 Typical microprofiles of oxygen, ammonium ion, nitrite, and nitrate concentrations in nitrifying aggregates, 76 5-4 Phylogenetic tree of AOB based on multiple alignment of 55 nearly full-length AOB 16S rDNA sequences, 79 5-5 Relationships of environmental partial 16S rRNA sequences to partial sequences from reference AOB, 80 5-6 Nitrosomonas europaea ATCC 25978; phase-contrast photomicrograph, 82 vii 5-7 Nitrosomonas species terrestrial strains; phase-contrast photomicrograph, 82 5-8 Nitrosomonas species sewer strain; phase-contrast photomicrograph, 83 5-9 Nitrosomonas species isolated from a drinking water reservoir; transmission electron micrograph, 83 5-10 Nitrosospira briensis negatively stained cell; electron micrograph, 83 5-11 Nitrosovibrio tenuis; phase-contrast micrograph, 83 5-12 Phylogenetic tree of NOB based on a multiple alignment of 40 NOB 16S rDNA sequences, 85 5-13 Neighbor-joining tree generated from an alignment of 168 rDNA sequences from NOB and other Proteobacteria, 86 5-14 Nitrobacter winogradskyi; phase-contrast photomicrograph, 87 5-15 Nitrococcus mobilis; phase-contrast photomicrograph, 87 5-16 Nitrospina gracilis; phase-contrast photomicrograph, 87 6-1 Generalized graph of Monod kinetics showing the relationship between the specific growth rate and half saturation coefficients for a single limiting substrate concentration, 102 6-2 Optimum temperature as a function of substrate concentration, 107 6-3 Maximum rate of oxidation as a function of substrate concentration, 107 6-4 Effect of pH on maximum specific growth rate of Nitrobacter species, 108 6-5 Effect of temperature and pH on un-ionized ammonia, 109 6-6 The pH dependence of the maximum-velocity coefficient for the first step of nitrification, 110 6-7 The pH dependence of the oxidation rate of the first step of nitrification, 110 6-8 Inactivation of nitrifying bacteria by monochloramine, 117 6-9 Relationship between the first-order inactivation rate constant and pH, 119 6-10 Data and fitted regression plots for BacLight based Nitrosomonas europaea inactivation experiments using the Chick–Watson model, 120 6-11 Distribution of mono- and dichloramine as a function of pH, 120 6-12 Distribution of hypochlorous acid and hypochlorite ion as a function of pH, 121 7-1 Organochloramine determination by subtraction, 134 7-2 Monochloramine concentrations by various methods, 134 7-3 HPC-plate count agar as an indicator of nitrification at various total chlorine and nitrite levels in a California distribution system, 142 viii 7-4 HPC-R2A as an indicator of nitrification at various total chlorine and nitrite levels in a California distribution system, 142 7-5 Relative counts: Plate count agar versus R2A agar in a Florida distribution system, 143 8-1 Utility practices and perceptions regarding prevention of nitrification, 154 8-2 Correlations between free ammonia, temperature, total chlorine residual, and nitrite concentration, 155 8-3 Example of an aqua ammonia 500-gal storage tank and metering pump, 157 8-4 Example of an anhydrous ammonia feed system, 157 8-5 Sodium hypochlorite and liquid ammonia feed system at a wellhead where chlorine is added first, 159 8-6 Calcium carbonate precipitation at injector and in-line mixing device, 160 8-7 Calcium carbonate precipitation removed from an ammonia injector, 160 8-8 Direct ammonia feed system, 162 8-9 Example of control schematic for chloramine formation, 163 8-10 Comparison of ammonia feed rates versus stock used, 165 8-11 Relationships between total chlorine residual and HPC levels, 167 8-12 Effect of pipe inlet orientation, horizontal versus vertical, in a 4-mil gal standpipe, 171 8-13 Recommended design change on storage tank inlet pipe to direct water flow vertically instead of horizontally for improved mixing, 171 8-14 The effect of inlet momentum on mixing characterisitcs of a 1-mil gal elevated storage tank using CFD modeling, 172 8-15 Difference in flow pattern and pipe velocity with conventional and unidirectional flushing, 176 8-16 Programmable blow-off next to a hydrant used to flush dead-end to increase residual, 178 8-17 Section of distribution pipe where extensive iron corrosion and nitrification were occurring, 178 8-18 Reduction in nitrite levels following water blending, 179 8-19 Correlation of pH and nitrite at a distribution system sampling location, 181 8-20 Comparison of chloraminated distribution waters in two Texas communities, 183 8-21 Survival of AOB as affected by chlorite ion, 183 9-1 Nitrification assessment flowchart, 193 ix