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WASTEWATER TREATMENT PLANT PUMPS: GUIDELINES FOR SELECTION, APPLICATION, AND OPERATION

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WASTEWATER TREATMENT PLANT PUMPS: GUIDELINES FOR SELECTION, APPLICATION, AND OPERATION

DEVELOPED BY The Hydraulic Institute

FIRST EDITION

Published by:

HYDRAULIC INSTITUTE Parsippany, New Jersey

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Wastewater Treatment Plant Pumps: Guidelines for Selection, Application, and Operation Copyright © 2015, by the Hydraulic Institute Printed in the United States of America Neither this book nor any part may be reproduced, transmitted, or distributed in any form or by any means, electronic or mechanical, or stored in a database, information storage, or retrieval system, without the prior written permission of the publisher. Direct requests to Permissions@pumps.org.

Reasonable portions may be reproduced or quoted as part of a review or other story about this publication.

Published by: HYDRAULIC INSTITUTE 6 Campus Drive, First Floor North Parsippany New Jersey 07054-4406 USA www.Pumps.org

Publication Data Wastewater Treatment Plant Pumps: Guidelines for Selection, Application, and Operation / Edited by Rodney Mrkvicka ...[et al]. -- 1st ed.

Includes bibliographical references and index.

ISBN 978-1-935762-37-9 This guideline has been created to provide engineers, trainers, maintenance staff, and plant operators with the knowledge necessary to effectively specify pumps in a typical aerobic wastewater treatment plant employing conventional activated sludge processes. It is not intended to provide guidelines for pumps used in wastewater collection systems that serve a wastewater treatment plant.

The intent of this guideline is to show the styles of pumps used in a typical aerobic wastewater treatment plant employing conventional activated sludge processes. It is not possible, nor is it the intent of this guideline, to cover all possible configurations of wastewater treatment plants and the styles of pumps within them. The guideline is primarily focused on pumps involved in the typical aerobic wastewater treatment plant employing conventional activated sludge processes.

NOTICE This publication was prepared by the Hydraulic Institute Wastewater Pumps Committee. Neither the Hydraulic Institute, its committees, nor any person acting on behalf of the Hydraulic Institute a.) makes any warranty, expressed or implied, with respect to the use of any information, apparatus, method, or process disclosed in the publication or guarantees that such may not infringe privately owned rights; b.) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in this publication. The Hydraulic Institute is in no way responsible for any consequences to a user or anyone else resulting from reference to these guidelines.

These guidelines do not contain a complete statement of all requirements and procedures necessary to ensure safe selection, application, and operation of wastewater treatment pumps.

Current printing (last digit): 10 9 8 7 6 5 4 3 2

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Table of Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

About the Hydraulic Institute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

About Pump Systems Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi xii xiv xv

Chapter • One Introduction, 1 1.1

Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.3

Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Chapter • Two Overview, 3 2.1

Objective of a Wastewater Treatment Plant . . . . . . . . . . . . . . . . . . . 3

2.2

What Is Wastewater? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3

Why Treat Wastewater? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.4

Biological Wastewater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.5

Process Treatment Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Chapter • Three Pump Selection Considerations and Guide Instructions, 11 3.1

Hydraulic Institute (HI) Standards and References. . . . . . . . . . . . . 13 3.1.1 HI Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1.2 HI Pump References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2

Site Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.1 Installation Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.2 Piping Alignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.3 Wet-well Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.4 Interior/Exterior Installations . . . . . . . . . . . . . . . . . . . . . . . .

3.2.5 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3

Pump Operational Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.3.1 Rate of Flow Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.3.2 Suction and Discharge Requirements . . . . . . . . . . . . . . . . . 20

15 15 15 19 19 19

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3.3.3 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.3.4 Type of Material Pumped . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.3.5 Additional Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.4

3.5

Asset Management, Life Cycle Cost, and Effective Procurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4.1 Asset Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4.2 Life Cycle Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4.3 Procurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34 34 35 35

Reliability, Preventive Maintenance, and Repair . . . . . . . . . . . . . . 36

Chapter • Four Treatment Plant Operations, 39 4.1

Collection System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

4.2

Treatment Plant Influent Headworks . . . . . . . . . . . . . . . . . . . . . . . 39 4.2.1 Pump Features and Considerations . . . . . . . . . . . . . . . . . . 40

4.3

Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4.3.1 Pump Features and Considerations . . . . . . . . . . . . . . . . . . 43

4.4

Grit Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.4.1 Pump Features and Considerations . . . . . . . . . . . . . . . . . . 45 4.4.2 Pump Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4.5

Primary Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.5.1 Primary Clarifier or Primary Sedimentation Tanks/Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.5.2 Primary Sludge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.5.3 Primary Scum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

47 48 50

4.6

Secondary Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6.1 Aeration Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6.2 Anoxic Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.6.3 Internal Recycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

51 51 53 55

4.7

Secondary Clarifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.7.1 Return Activated Sludge (RAS) . . . . . . . . . . . . . . . . . . . . . 56 4.7.2 Waste Activated Sludge (WAS) . . . . . . . . . . . . . . . . . . . . . 57

4.8

Secondary Scum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

4.9

Tertiary Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.9.1 Filter Backwash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.9.2 Backwash Wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

47

4.10 Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.10.1 Pump Features and Considerations . . . . . . . . . . . . . . . . . . 61 4.11 Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.11.1 Chlorination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

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4.11.2 Ultraviolet Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.11.3 Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.12 Effluent Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.12.1 Effluent Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.12.2 Plant Nonpotable Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.12.3 Water Reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.12.4 Groundwater Recharge Application. . . . . . . . . . . . . . . . . . .

64 64 65 66 66

4.13 Chemical Feed Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.13.1 Pump Features and Considerations . . . . . . . . . . . . . . . . . . 68 4.14 Other Pumping Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.14.1 Sump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.14.2 Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.15 Sludge Handling and Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.15.1 Sludge Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.15.2 Sludge Thickener. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.15.3 Digester and Digested Sludge. . . . . . . . . . . . . . . . . . . . . . .

72 72 73 73

4.16 Dewatering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 4.16.1 Sludge Transfer Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.16.2 Dewatering Feed Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Chapter • Five Pump Drivers, 77 5.1

Motor Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1.1 Open Drip-proof (ODP) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1.2 Totally Enclosed Fan Cooled (TEFC) . . . . . . . . . . . . . . . . .

5.1.3 Totally Enclosed Nonventilated (TENV) . . . . . . . . . . . . . . .

5.1.4 Weather Protected Types I and II (WPI, WPII) . . . . . . . . . .

5.1.5 Explosion-proof Motors (XP) . . . . . . . . . . . . . . . . . . . . . . . .

5.1.6 Immersible Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1.7 Submersible Motors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

77 78 78 79 79 79 79 80

5.2

Motor Starting Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.2.1 Across-the-Line or Direct-on-Line (DOL) . . . . . . . . . . . . . . .

5.2.2 Reduced Voltage Soft Starters (RVSS) . . . . . . . . . . . . . . . .

5.2.3 Variable Frequency Drives (VFDs) . . . . . . . . . . . . . . . . . . .

5.2.4 Application Considerations (Solid-state Starting Methods) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

80 80 81 82

Pump Motor Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.1 Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.2 Level Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.3 Flow Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.4 Pressure Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.3.5 Process Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

84 84 84 85 85 85

5.3

83

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Appendix A Pump Selection Summary Table, 87 Appendix B Pump Materials of Construction, 95 Appendix C Mechanical Seals and Packing Used with Wastewater Treatment Plant Pumps, 103 C.1 Mechanical Seals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 C.2 Packing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 C.3 Single and Split Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 C.4 Piping Plans and Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 C.4.1 Single Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 C.4.2 Dual Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 C.5 Pump Construction Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Appendix D Couplings, 117 Appendix E Image Credits, 119 Appendix F Bibliography, 121 Appendix G Glossary, 123 Appendix H Index, 131 List of Figures 2.1

Conventional wastewater treatment plant flow diagram . . . . . . . . . 8

2.2

Conventional wastewater treatment plant with clarifiers flow diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

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3.1

Pump selection guide chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.2

Rotodynamic pump types – overhung impeller . . . . . . . . . . . . . . . 16

3.3

Rotodynamic pump types – between bearings . . . . . . . . . . . . . . . 17

3.4

Rotodynamic pump types – vertically suspended . . . . . . . . . . . . . 18

3.5

Recommended maximum operating speeds for single suction pumps (US customary units) with Nss (S) = 8500 . . . . . . . 27

3.6

Recommended maximum operating speeds for single suction pumps (metric units) with S (Nss) = 165 . . . . . . . . . . . . . . 28

4.1

Influent pump station arrangement . . . . . . . . . . . . . . . . . . . . . . . . 40

4.2

Horizontal solids-handling pump . . . . . . . . . . . . . . . . . . . . . . . . . . 42

4.3

Vertical solids-handling pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.4

Grit removal system and pump . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

4.5

Grit removal and processing system . . . . . . . . . . . . . . . . . . . . . . . 44

4.6

Multiple clarifier basin arrangement . . . . . . . . . . . . . . . . . . . . . . . . 47

4.7

Clarifier basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.8

Solids processing pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.9

Aeration basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

ix

4.10 Submersible pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.11 Submersible recycle pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.12 Typical UV lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.13 Typical ozone generator unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.14 Chemical feed pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.15 Chemical feed pump assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.16 Typical sump pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.17 Typical sample pump and container . . . . . . . . . . . . . . . . . . . . . . . 71 4.18 Solids-handling pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.1

Typical induction motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

C.1

Typical mechanical seal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

C.2

Single cartridge pusher seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

C.3

Elastomer bellows seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

C.4

Split mechanical seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

C.5

Plan 02. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

C.6

Plan 03. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

C.7

Plan 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

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C.8

Plan 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

C.9

Plan 32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

C.10 Plan 54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 C.11 Component dual seal for submersible solids-handling pump . . . 116

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Foreword Access to clean water is essential to sustain and provide for the continued development of the world’s population and its economic growth. One of the most urgent concerns today is to have sufficient supplies of clean water to meet and sustain a constantly growing demand. The water industry, including needs for the transfer and treatment of sewage and stormwater, continue to evolve. Purifying used water before discharging it back into the environment dates back to the 19th century. Now, the US Environmental Protection Agency (EPA) estimates that wastewater facilities in the United States treat 36 billion cubic meters (9.5 trillion gallons) of wastewater per year, and an estimated 15,000 publicly-owned treatment plants provide wastewater collection, treatment, and disposal service to more than 226 million people.

Today, the treatment process is guided by extensive engineering and technological development, which continues to refine the process. Wastewater treatment is, and has been, an essential process to mitigate the effects of municipal, industrial, and agricultural by-products. However, new strategies are being developed and implemented to utilize the resource potential of wastewater. These strategies go beyond discharging treated water back in to the environment. They call for reusing and recycling the water to maintain or increase consumable supplies, while treatment process by-products are recovered as energy resources. Traditional “wastewater treatment plants” of the 20th century are transitioning into 21st century “water resource recovery facilities” as we find ways to optimize the process and fully harness the recovered nutrients.

Concurrently, in an ever-increasingly energy-efficiency conscious world, reducing the energy required to complete the treatment process and the valuable water recovery activities is critical. Nearly 2% of total US electricity consumption goes towards moving and treating water and wastewater. The pumping systems employed at wastewater treatment plants typically consume 10-15% of plant energy. Thus, poor application of the pumps, flow

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control, and motors can lead to inefficiency and wasted energy consumption. Optimizing pumping application and operations is increasingly fundamental.

Wastewater Treatment Plant Pumps: Guidelines for Selection, Application, and Operation is intended to assist in understanding the general layout, components, and operation of a typical wastewater treatment plant, and provide the guidance necessary to select pump types and define pump materials to perform effectively, efficiently, and reliably in the various plant operations. In addition to pump selection criteria, this document also addresses auxiliary components that are required to operate a pump, including the driver, couplings, and control methods. This single resource yields the practical information for those that are new to defining treatment plant pumping systems and equipment, and for those that are experienced the field but desire to enhance their knowledge-base of these systems.

This guideline applies to pumps used in a typical wastewater treatment plant normally operated today in the United States. It is not possible, nor is it the intent of this guideline, to cover all possible configurations, components, or specialized treatment plant processes. Any change in plant operation defined herein will affect the selection of the proper pumping systems.

This guideline presents the collective knowledge of numerous pump and wastewater design industry experts, who collectively possess hundreds of years of practical experience. It is their intention to assist the reader by presenting this information in one easy to follow guideline, and provide the information necessary to the reader to make selections to optimize systems efficiently, reliably, and economically.

This guideline assumes that the reader has a basic familiarity with engineering principles and practices; it is not intended to be a complete design manual for a wastewater treatment plant. It is recommended that the reader reference additional detailed material, communicate with the designers and operators of the plant, and define the operating requirements of the plant as required to confirm and evaluate all final pump and pump component selections.

Acknowledgements The Hydraulic Institute (HI), the largest trade association of North American pump manufacturers and supplier companies, who provide the pumping industry with ancillary parts, equipment, and services, gratefully acknowledges the exceptional efforts demonstrated by the Hydraulic Institute Wastewater Pumps Committee chairs and members in researching the technical material, developing the text, and furnishing the graphics and photographs that they have incorporated in this important contribution to the industry.

The Hydraulic Institute Wastewater Pumps Committee and the development of this document were led by Rodney Mrkvicka, P.E. (Committee Chair) and Ernie Sturtz, P.E. (Committee Vice-Chair). They provided vision, guidance, and maintained the development process to complete this

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document. Keeping the HI Standards and Systems Committee goals for guideline documents in perspective, they kept the document development progressing, developed original material, and managed additional information contributed by the committee. They also led the committee in discussions to resolve any differences in opinion, resolved all comments received during the development and review process, and to agreement on the final content. The committee members listed below provided valuable contributions and a dedicated effort in the completion of this document. Special recognition is also given to the members of the HI Seals Committee for their detailed contribution to this guideline. Our appreciation is also extended to Mick Cropper (Vice President – Technical Affairs) for his guidance and suggestions based on his experience with the development of a previous application guideline for HI. Hydraulic Institute Wastewater Pumps Guideline Committee Rodney Mrkvicka, Committee Chair Smith & Loveless Inc.

Ralph Gabriel John Crane Inc.

Ernie Sturtz, Committee ViceChair CDM Smith

Patrick Hogg Nidec-US Motors

Julian Atchia SJE-Rhombus®

Eric Olsen Mechanical Solutions Inc.

Henri Azibert Fluid Sealing Association

Jan Schyberg Xylem Inc. – Water Solutions

Ulf Carlsson Xylem Inc.

Constantino Senon MWH Americas Inc.

Greg Case TACO Inc.

George Tey MWH Americas Inc.

Jack Creamer Schneider Electric – Square D

Thiru Veeraraghaven A.W. Chesterton Company

Steve Fehniger CDM Smith

Don Weidemann Neptune Chemical Pump Co., Inc.

In addition, special recognition is provided to Robert Asdal, HI Executive Director, and the staff of the Hydraulic Institute, specifically Gregg Romanyshan, HI Technical Director; Peter Gaydon, HI Standards Engineering Director; and Denielle Giordano, HI Technical Committee Administrator, for their experience and assistance during the committee meetings and in the development of this document. Their support, contributions, patience, and dedication were invaluable, greatly appreciated, and has led to the successful publication of this document.

Several independent experts in the industry provided their time to review and evaluate the committee draft. They conducted a thorough review of the

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material, ensuring the document met the intended goal established by the committee chairs, and provided accurate, coordinated, and relevant information to the reader. Their efforts were extremely valuable, and the committee thanks all of them for their time and efforts.

Special Acknowledgements – Document Review John Anspach John Anspach Consulting

John Kelly Smith & Loveless Inc.

Tryg Dahl Intelliquip

Ben Mosher CDM Smith

Richard Grubbs Chevron

Darby Ritter Smith & Loveless Inc.

Greg Harem Gray & Osborne

Dr. Roger Stephen MWH Global

Brian Karmasin CDM Smith

About the Hydraulic Institute The mission of the Hydraulic Institute is to be a value-adding resource to member companies, engineering consulting firms, and pump users worldwide by developing and delivering comprehensive industry standards, expanding knowledge by providing education and tools for the effective application, testing, installation, operation, maintenance, and performance optimization of pumps and pumping systems, and by serving as a forum for the exchange of industry information. For more information on the Hydraulic Institute, its member companies, and its Standards Par tners, visit www.Pumps.org.

Hydraulic Institute 6 Campus Drive 1st Floor, North Parsippany, NJ 07054 Phone: (973) 267-9700 Fax: (973) 267-9055 www.Pumps.org

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About Pump Systems Matter Pump Systems Matter (PSM) is a nonprofit 501(c)3 educational affiliate of the Hydraulic Institute with the vision of being the leading training authority on pumps and pumping systems. PSM’s mission is to provide product-neutral training on energy efficiency, reliability, economics, and effective application of pump systems. PSM currently offers over 20 courses relating to energy efficiency, pump technology, and systems in various formats including classroom instruction, online webinars, and e-learning opportunities.

PSM partners with key groups such as the energy efficiency community, utilities, engineering consulting firms, pump system users, the Hydraulic Institute, and other associations and government agencies. PSM strategically supports educating, encouraging, and creating incentives for end users and trade partners to adopt systems optimization products, services, and practices by building awareness that energy efficiency and reliability go hand in hand.

Pump Systems Matter 6 Campus Drive 1st Floor, North Parsippany, NJ 07054 Phone: (973) 267-9700 Fax: (973) 267-9055 www.PumpSystemsMatter.org

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CHAPTER • ONE

Introduction 1.1 Purpose This document provides application guidelines for the selection of pumps used in a typical aerobic wastewater treatment plant employing conventional activated sludge processes. It is not intended to provide guidelines for pumps used in wastewater collection systems that serve a wastewater treatment plant.

The basic process operations used in a typical aerobic wastewater treatment plant are discussed in this guideline, as are the application and operation of rotodynamic and positive displacement pumps for the various processes. Each section will include a brief description of the particular process operation and the recommended type of pump, including materials of construction and pump sealing recommendations, to be applied to that particular process.

1.2 Scope This guideline will cover the typical treatment process in an aerobic wastewater treatment plant, from plant influent to effluent discharge. It also will include the related processes to the wastewater treatment scheme, such as sludge transfer and dewatering, chemical feed, sampling, and plant water systems. The guideline is based on the typical plant having a treatment capacity range defined as 10 to 100 million gallons per day (mgd), and the facility being the conventional activated sludge type.

The guideline will define the processes included for a complete treatment plant. However, each individual process discussion can be used for pump application guidelines.

This guideline includes a treatment process flowchart of the wastewater treatment processes, with each process being defined. Refer to this

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Wastewater Treatment Plant Pumps

flowchart to understand the relationship between the various process operations.

Each process operation section will include a brief description of the particular operation as well as a description of the pumping process taking place, special considerations when applying pumps in this process, and a listing of the type of pump recommended for use.

An applications spreadsheet is included to aid in summarizing the process operation, pump application characteristics, and recommended pump units to be used. It is recommended that the user read the information provided in the individual sections to understand the considerations in applying the pumps in that operation.

1.3 Disclaimer This document does not purport to cover all treatment applications or the complete treatment process system included in a plant, but has endeavored to provide an example that may be helpful in addressing the selection of pumps for typical treatment plant operations. The user will need to understand the actual application and its operational characteristics and use this manual as general guidance for selecting pumps to service that operation.

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CHAPTER • TWO

Overview 2.1 Objective of a Wastewater Treatment Plant Water, just like air, is essential for living. We need fresh, clean water for human and animal consumption, to support aquatic life, for generating power, to irrigate crops, and for water-based recreation. Even though approximately two thirds of the earth’s surface is covered by water, most of it is not potable, i.e., cannot be used as drinking water.

The supply of fresh (potable) water is taken for granted in many locations, as if it were a nondepletable resource. However, the world’s supply of freshwater is slowly decreasing. Much of the world’s population is already dealing with the problem of freshwater scarcity, although it may not be widely known. Water scarcity is among the most serious crises facing the world. While some of the freshwater supply problems are based on nature, the fact is that water supply decline can be attributed to increasing consumption, wasting of sources, and potable water sources being contaminated by pollutants. Freshwater is consumed, wasted, and polluted at greater rate than it is regenerated by natural processes. The world needs to become more water-efficient, and methods to accomplish that include treating polluted sources to recover water and to recycle and reuse wastewater.

The purposes of wastewater treatment system operations are to provide controlled removal and/or decomposition of wastewater constituents so that odor nuisances will not arise, and pollution of valuable water resources and hazards to the community's health will be reduced.

2.2 What Is Wastewater?

Potable water is defined as a water source that can be consumed by humans and does not contain high levels of any compounds that cause illness or disease. Potable water sources become wastewater (or sewage) after they are contaminated with natural or synthetic microbiological compounds

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Wastewater Treatment Plant Pumps

and organic/inorganic compounds. Wastewater is defined as the waterborne waste material of a community that includes all normal wastes from human activities and residences, as well as many forms of waste matter and compounds from industries and commercial establishments. The compounds may enter the water stream in many ways, including contamination in surface water, groundwater, and stormwater. Wastewater can also be termed grey water or black water.

Grey water is defined as untreated household wastewater that has not come into contact with toilet waste. Grey water includes used water from bathtubs, showers, bathroom wash basins, clothes washers, and laundry tubs. It does not include wastewater from kitchen sinks or dishwashers (see reference 6 in Bibliography). Black water refers to wastewater that contains contaminates, including sewage from toilets and sanitary fixtures.

The terms domestic sewage and sanitary sewage are normally used to identify sewage containing a majority of residential household and human body waste matter, and less or no waste from industrial or commercial processes.

Domestic sewage should also be distinguished from stormwater or storm drainage. Stormwater is the runoff of water from impervious surfaces (such as streets, roofs, paved areas, or developed grounds) that occurs during precipitation events or from snow and ice melting. This water does not naturally infiltrate or absorb into the ground or plants. Areas that are more developed and include larger paved areas typically will create a larger stormwater contribution. The stormwater can collect a large amount of pollutants that are contained on the many surfaces, including debris, oils, sanitary wastes from animals, and fertilizer and pesticide runoff from lawns and fields.

A combined sewer system collects the sanitary sewer contribution and the stormwater contribution in a single collection system. The contribution of the storm flow can vary widely, depending on the precipitation event and the area of runoff. The difference between dry weather flow and wet weather flow is termed a peaking factor. This factor must be known when evaluating the plant and pumping capacities so they can handle the peak flows without causing backups or overflows. Some storm flows are collected and held to prevent a high peak flow to the treatment plant and prevent overloading the plant hydraulics. This stored flow is transferred to the treatment plant in a controlled manner after the storm event concludes.

Combined sewer systems are no longer designed when building new collection systems. However, many older areas were constructed with this type of system and are still using this system today.

Domestic sewage should also be distinguished from industrial waste or wastewater from commercial or manufacturing enterprises. Residential wastewater is a type of wastewater generated from people and rooms in a household with fixtures. The volume and type of wastewater varies from each home and region based on factors such as the number of water-using fixtures, appliances, number of occupants and their ages, and their living habits. But when compared to the variety of wastewater flows generated by

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different nonresidential sources, residential wastewater shares many similar characteristics overall.

Nonresidential wastewater in communities is generated by diverse sources, such as office buildings, businesses, markets, restaurants, schools, hospitals, farms, manufacturers, and other commercial, industrial, and institutional entities. Stormwater is a nonresidential source and carries trash and other pollutants from streets, buildings, and parking lots, as well as fertilizers and pesticides from yards and fields.

Because of the different nonresidential wastewater characteristics, it is recommended that each source be individually assessed. As an example, public facilities may generate wastewater with similar characteristics to domestic sewage, but usually at higher volumes and at different hours. The volume and pattern of flows from rental properties, hotels, and recreation areas will vary seasonally. Laundries differ because they produce high volumes of wastewater containing fibers and surfactants.

Wastewater from some sources may require pretreatment prior to the flow being discharged to a municipal wastewater treatment facility. Examples are restaurants, which typically generate oil and grease. It may be necessary to provide pretreatment of oil and grease prior to treating the wastewater flow. Also, industries can produce a wastewater that is high in chemical and biological pollutants. This high treatment load can cause operational difficulties at the community treatment plant. Communities may require these types of sources to provide their own treatment of the waste or a pretreatment step before discharging the flow from their facility.

Industrial waste varies widely in character, in contrast to the fairly uniform characteristics of domestic sewage, and usually requires special treatment processes. The sewer systems of many communities carry a mixture of domestic sewage and industrial wastes.

Both domestic and industrial wastewater contain both inorganic and organic types of solids. The inorganic and organic solids exist in soluble and insoluble forms. The soluble inorganic solids include mineral ions in solution, such as sodium, potassium, iron, and calcium. Some of these dissolved solids exist in the water supply and some are added to the water when it is used. The insoluble inorganic solids found in wastewater include such things as sand, clay, and other inert or salt materials. The insoluble inorganic solids can be removed in a screening, settling, or filtration process; become incorporated in the mixed liquor solids; or some may pass through the treatment plant.

Wastewater will also contain many fibrous or stringy materials, which have normally consisted of strings, rags, paper, and hair. Additional fibrous and stringy materials are now becoming more prevalent in wastewater flows. These items include personal wipes, towels, cleaning cloths, and household cleaning materials (which include a woven fabric) that are being marketed and sold to be discarded through the sewer system. Such items are made to resist tearing so they can serve their purpose, but they are difficult to cut or reduce into smaller pieces so they can be pumped. These items, along with other stringy materials and rags, can bind together

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Wastewater Treatment Plant Pumps

creating a large mass, which can potentially lead to clogging issues in the pump and associated piping.

A wide variety of organic solids are found in wastewater. Like inorganic solids, some of the organic solids are soluble and others are insoluble.

Some of the organic solids are readily decomposable and others will decompose only slightly or not at all. The portion of organic material that is decomposable is commonly referred to as biodegradable material. The term biodegradable simply means that the organic material can be biologically broken down or stabilized by bacterial action. Wastewater strength is usually measured by the amount of decomposable or biodegradable material it contains.

The term biochemical oxygen demand (BOD) refers to the amount of oxygen used as the biodegradable wastewater fraction that is decomposed by bacteria and other microscopic organisms, hence it indicates the "strength" of the wastewater or the concentration of microbial food in wastewater. The greater the amount of biodegradable organic material in the wastewater, the greater the BOD. Wastewater is generated by almost all of the residential and nonresidential sources in a community. Unless properly treated to remove contaminates, wastewater can harm public health and the environment.

2.3 Why Treat Wastewater?

Wastewater needs to be treated so that it does not have an adverse effect on the environment or the humans and animals that require water to live.

Since the solid and liquid waste products of humans are largely organic in nature, they will putrefy or decompose. If the putrefaction or decomposition process is not controlled, it produces obnoxious odors, and may cause destruction of the recreational, agricultural, and public water supplies into which the wastewater may drain. Most important of all, improper waste treatment may create a serious threat to the health of the community.

Various microorganism species contained in wastewater can have adverse impacts on human health. Outbreaks of diseases can occur as a result of drinking polluted water, eating contaminated fish, or indulging in recreational activities in polluted water bodies. Animals and insects that come in contact with wastewater can spread illnesses as well.

Large concentrations of degradable organic material in wastewater are dangerous to water sources such as lakes, streams, and oceans, because organisms consume the dissolved oxygen contained in the water in the process of degrading the waste. This process reduces, and can deplete, the supply of oxygen in the water, which is needed by aquatic life to survive.

The depletion of the oxygen in the water can result in fish kills, increased odors, and overall deterioration of the water quality.

Some organic compounds are more stable than others and cannot be quickly broken down by organisms. This poses an additional challenge for treatment. This is true with many synthetic organic compounds developed for agriculture and industry. Some of the synthetic organic compounds that

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are included in pesticides, herbicides, dyes, pigments, chemicals, and oils are toxic to humans, fish, and aquatic plants. At times these compounds have been disposed of improperly in drains or carried in stormwater. In the receiving water bodies, they kill or contaminate fish, making them unfit to eat. Other causes of toxicity to life are caused by wastewater contamination, including cyanide, sulfides, phenols, surfactants, and heavy metals, such as copper, zinc, and chromium that are contained in wastewater sources.

2.4 Biological Wastewater Treatment The decomposable organic material or microbial food in wastewater is stabilized in a wastewater treatment system by the action of microorganisms, primarily bacteria. Bacteria use the decomposable organic material for food. When the bacteria consume the organic material in the waste stream, they obtain the energy required to sustain life and the chemical building blocks required to generate new cells. This consumption of soluble organic material by bacteria converts the soluble material to insoluble cell mass that can be removed by settling or other means. This is the basic mechanism by which all biological waste treatment systems operate, that is, the biological conversion of organic material to energy and new cells.

The bacteria use dissolved oxygen as they metabolize the organic material. Inorganic end products, water, carbon dioxide, nitrates, and sulfates result from this process. A portion of the food is converted to new bacteria.

This reaction is called synthesis, where the organic material is changed from one form, soluble organic material, to another form, insoluble cells.

As the wastewater travels through the plant, it will be treated to remove its pollutants. Therefore, the characteristics of the water will change depending on the various steps of the treatment process that have been completed. In general, the primary portion of the treatment process will have removed the heavier solids that settle, and the fats, oils, and greases that will float. The secondary treatment portion addresses dissolved and floating biological matter in the water. Tertiary treatment will provide further removal of dissolved or suspended matter. Secondary and tertiary treatment can require the addition of chemicals to enhance the treatment process.

2.5 Process Treatment Scheme Figures 2.1 and 2.2 indicate the flow path of the wastewater and the other related flow streams through a conventional, municipal, activated sludge, wastewater treatment plant. The figures identify the processes used, how the processes relate to each other, and also list the pump types for each process for the types of plant variations. These figures can assist the reader in understanding how the various treatment plant process components interact together and how the pumps are transferring flow between the processes.

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