biosolids engineering and management

This book Volume 7 covers the topics of sludge and biosolids transport,pumping and storage, sludge conversion to biosolids, waste chlorination forstabilization, regulatory requirements,

Handbook of Environmental Engineering Series

Volume 1: Air Pollution Control Engineering L K Wang, N C Pereira, and Y T Hung (eds.)

H ANDBOOK OF E NVIRONMENTAL E NGINEERING

Biosolids Engineering

and Management

Edited by

Lenox Institute of Water Technology, Lenox, MA

Krofta Engineering Corporation, Lenox, MA Zorex Corporation, Newtonville, NY

Lenox Institute of Water Technology, Lenox, MA

Krofta Engineering Corporation, Lenox, MA

Department of Civil and Environmental Engineering

Cleveland State University, Cleveland, OH

Dean & Director (retired), Lenox Institute of Water Technology

Assistant to the President, Krofta Engineering Corporation

Vice President, Zorex Corporation

1 Dawn Drive, Latham, NY 12110 USA

larrykwang@juno.com

lawrencekwang@gmail.com

Nazih K Shammas

Professor and Environmental Engineering Consultant

Ex-Dean and Director, Lenox Institute of Water Technology

Advisor, Krofta Engineering Corporation

35 Flintstone Drive, Pittsfield, MA 01201, USA

n.shammas@shammasconsult.com

nazih@n-shammas.org

Yung-Tse Hung

Professor, Department of Civil and Environmental Engineering

Cleveland State University

16945 Deerfield Drive, Strongsville, OH 44136, USA

y.hung@csuohio.edu

ISBN 978-1-58829-861-4 e-ISBN 978-1-59745-174-1

Library of Congress Control Number: 2008922724

c

2008 Humana Press, a part of Springer Science+Business Media, LLC

All rights reserved This work may not be translated or copied in whole or in part without the written permission of the publisher (Humana Press, 999 Riverview Drive, Suite 208, Totowa, NJ 07512 USA), except for brief excerpts in connection with reviews or scholarly analysis Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden.

The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified

as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made The publisher makes no warranty, express or implied, with respect to the material contained herein.

Printed on acid-free paper

9 8 7 6 5 4 3 2 1

springer.com

dent of Humana Press, who encourged and vigorously supported the editors and many contributors around the world to embark on this ambitious, life-long handbook project (1978–2009) for the sole purpose of protecting our environment, in turn, benefiting our entire mankind.

The past thirty years have seen a growing desire worldwide that positiveactions be taken to restore and protect the environment from the degradingeffects of all forms of pollution—air, water, soil, and noise Since pollution is

a direct or indirect consequence of waste, the seemingly idealistic demand for

“zero discharge” can be construed as an unrealistic demand for zero waste.However, as long as waste continues to exist, we can only attempt to abatethe subsequent pollution by converting it to a less noxious form Three majorquestions usually arise when a particular type of pollution has been identified:(1) How serious is the pollution? (2) Is the technology to abate it available? (3) Dothe costs of abatement justify the degree of abatement achieved? This book is one

of the volumes of the Handbook of Environmental Engineering series The principal

intention of this series is to help readers formulate answers to the above threequestions

The traditional approach of applying tried-and-true solutions to specific lution problems has been a major contributor to the success of environmen-tal engineering and has accounted in large measure for the establishment of

pol-a “methodology of pollution control.” However, the repol-alizpol-ation of the increasing complexity and interrelated nature of current environmental prob-lems renders it imperative that intelligent planning of pollution abatementsystems be undertaken Prerequisite to such planning is an understanding ofthe performance, potential, and limitations of the various methods of pollutionabatement available for environmental scientists and engineers This series ofhandbooks reviews at a tutorial level a broad spectrum of engineering systems(processes, operations, and methods) currently being utilized, or of potentialutility, for pollution abatement We believe that the unified interdisciplinaryapproach presented in these handbooks is a logical step in the evolution ofenvironmental engineering

ever-Discussion of the various engineering systems presented shows how anengineering formulation of the subject flows naturally from the fundamentalprinciples and theories of chemistry, microbiology, physics, and mathematics.This emphasis on fundamental science recognizes that engineering practicehas in recent years become more firmly based on scientific principles ratherthan on its earlier dependency on empirical accumulation of facts It is notintended, though, to neglect empiricism where such data lead quickly to themost economic design; certain engineering systems are not readily amenable tofundamental scientific analysis, and in these instances we have resorted to lessscience in favor of more art and empiricism

Since an environmental engineer must understand science within the context

of application, we first present the development of the scientific basis of aparticular subject, followed by exposition of the pertinent design concepts andoperations, and detailed explanations of their applications to environmental

vii

quality control or remediation Throughout the series, methods of practicaldesign and calculation are illustrated by numerical examples These examplesclearly demonstrate how organized, analytical reasoning leads to the most directand clear solutions Wherever possible, pertinent cost data have been provided.Our treatment of pollution-abatement engineering is offered in the belief thatthe trained engineer should more firmly understand fundamental principles, bemore aware of the similarities and differences among many of the engineeringsystems, and exhibit greater flexibility and originality in the definition andinnovative solution of environmental pollution problems In short, the environ-mental engineer should by conviction and practice be more readily adaptable tochange and progress.

Coverage of the unusually broad field of environmental engineering hasdemanded an expertise that could only be provided through multiple authors.The authors use their customary personal style in organizing and presentingtheir topics; consequently, the topics are not discussed in a homogeneous man-ner Moreover, owing to limitations of space, some of the authors’ topics couldnot be discussed in great detail, and many less important topics had to be merelymentioned or commented on briefly All authors have provided an excellent list

of references at the end of each chapter for the benefit of the interested readers

As each chapter is meant to be self-contained, some mild repetition amongthe various texts was unavoidable In each case, all omissions or repetitionsare the responsibility of the editors and not the individual authors With thecurrent trend toward metrication, the question of using a consistent system ofunits has been a problem Wherever possible, the authors have used the Britishsystem (fps) along with the metric equivalent (mks, cgs, or SIU) or vice versa.Conversion factors for environmental engineers are attached as an appendix inthis handbook for the convenience of international readers The editors sincerelyhope that this duplication of units will prove to be useful to the reader

The goals of the Handbook of Environmental Engineering series are (1) to cover

entire environmental fields, including air and noise pollution control, solidwaste processing and resource recovery, physicochemical treatment processes,biological treatment processes, biosolids management, water resources, naturalcontrol processes, radioactive waste disposal, and thermal pollution control; and(2) to employ a multimedia approach to environmental pollution control sinceair, water, soil, and energy are all interrelated

As can be seen from the above handbook coverage, no consideration is given

to pollution by type of industry, or to the abatement of specific pollutants.Rather, the organization of the handbook series has been based on the threebasic forms in which pollutants and waste are manifested: gas, solid, and liquid

In addition, noise pollution control is included in the handbook series

This book, volume 7, Biosolids Engineering and Management, is a sister book to volume 6, Biosolids Treatment Processes Both biosolids books have been designed

to serve as basic biosolids treatment textbooks as well as comprehensive erence books We hope and expect they will prove of equally high value toadvanced undergraduate and graduate students, to designers of wastewater,

ref-biosolids, and sludge treatment systems, and to scientists and researchers Theeditors welcome comments from readers in all of these categories It is our hopethat both books will not only provide information on the physical, chemical, andbiological treatment technologies, but also serve as a basis for advanced study

or specialized investigation of the theory and practice of individual biosolidsmanagement systems

This book (Volume 7) covers the topics of sludge and biosolids transport,pumping and storage, sludge conversion to biosolids, waste chlorination forstabilization, regulatory requirements, cost estimation, beneficial utilization,agricultural land application, biosolids landfill engineering, ocean disposaltechnology assessment, combustion and incineration, and process selection forbiosolids management systems The sister book (Volume 6) covers topics onbiosolids characteristics and quantity, gravity thickening, flotation thickening,centrifugation, anaerobic digestion, aerobic digestion, lime stabilization, low-temperature thermal processes, high-temperature thermal processes, chemicalconditioning, stabilization, elutriation, polymer conditioning, drying, belt filter,composting, vertical shaft digestion, flotation, biofiltration, pressurized ozona-tion, evaporation, pressure filtration, vacuum filtration, anaerobic lagoons, ver-micomposting, irradiation, and land application

The editors are pleased to acknowledge the encouragement and supportreceived from their colleagues and the publisher during the conceptual stages

of this endeavor We wish to thank the contributing authors for their time andeffort, and for having patiently borne our reviews and numerous queries andcomments We are very grateful to our respective families for their patience andunderstanding during some rather trying times

Lawrence K Wang, Lenox, MA Nazih K Shammas, Lenox, MA Yung-Tse Hung, Cleveland, OH

Preface vii

Contributors xxi

1 Transport and Pumping of Sewage Sludge and Biosolids Nazih K Shammas and Lawrence K Wang 1

1 Introduction 1

1.1 Sewage Sludge and Biosolids 1

1.2 Biosolids Applications 2

1.3 Transport and Pumping of Sewage Sludge and Biosolids 2

2 Pumping 2

2.1 Types of Sludge and Biosolids Pumps 3

2.2 Application and Performance Evaluation of Sludge and Sludge/Biosolids Pumps 12

2.3 Control Considerations 14

3 Pipelines 18

3.1 Pipe, Fittings, and Valves 18

3.2 Long-Distance Transport 18

3.3 Headloss Calculations 21

3.4 Design Guidance 22

3.5 In-Line Grinding 26

3.6 Cost 26

4 Dewatered Wastewater Solids Conveyance 28

4.1 Manual Transport of Screenings and Grit 29

4.2 Belt Conveyors 29

4.3 Screw Conveyors 32

4.4 Positive-Displacement–Type Conveyors 33

4.5 Pneumatic Conveyors 33

4.6 Chutes and Inclined Planes 36

4.7 Odors 36

5 Long-Distance Wastewater Solids Hauling 36

5.1 Truck Transportation 37

5.2 Rail Transportation 42

5.3 Barge Transportation 47

5.4 Design of Sludge/Biosolids Hauling 51

5.5 Example 54

6 Potential Risk to Biosolids Exposure 55

6.1 Biosolids Constituents that Require Control of Worker Exposure 56

6.2 Steps to Be Taken for Protection of Workers 57

Nomenclature 59

References 60

Appendix 64

2 Conversion of Sewage Sludge to Biosolids Omotayo S Amuda, An Deng, Abbas O Alade, and Yung-Tse Hung 65

1 Introduction 65

1.1 Sewage and Sewage Sludge Generation 65

1.2 Composition and Characteristics of Sewage 66

1.3 Sewage and Sewage Sludge Treatment 68

1.4 Biosolids Regulations 70

xi

2 Sewage Clarification 72

2.1 Sedimentation Clarification 72

2.2 Flotation Clarification 72

2.3 Membrane Clarification 73

3 Sewage Sludge Stabilization 73

3.1 Aerobic Stabilization 74

3.2 Alkaline Stabilization 75

3.3 Advanced Alkaline Stabilization 77

3.4 Anaerobic Digestion 77

3.5 Composting 84

3.6 Pasteurization 86

3.7 Deep-Shaft Digestion 87

4 Conditioning 87

4.1 Chemical Conditioning 87

4.2 Heat Conditioning 88

4.3 Cell Destruction 89

4.4 Odor Conditioning 90

4.5 Electrocoagulation 91

4.6 Enzyme Conditioning 92

4.7 Freezing 92

5 Thickening 93

5.1 Gravity Thickening 93

5.2 Centrifugation Thickening 95

5.3 Gravity Belt Thickening 97

5.4 Flotation Thickening 97

5.5 Rotary Drum Thickening 97

5.6 Anoxic Gas Flotation Thickening 97

5.7 Membrane Thickening 99

5.8 Recuperative Thickening 100

5.9 Metal Screen Thickening 100

6 Dewatering and Drying 100

6.1 Belt Filter Press 100

6.2 Recessed-Plate Filter Press 101

6.3 Centrifuges 103

6.4 Drying Beds 104

6.5 Vacuum Filtration 106

6.6 Electro-Dewatering 107

6.7 Metal Screen Filtration 107

6.8 Textile Media Filtration 108

6.9 Membrane Filter Press 109

6.10 Thermal Conditioning and Dewatering 109

6.11 Drying 109

7 Other Processes 113

7.1 Focused Electrode Leak Locator (FELL) Electroscanning 113

7.2 Lystek Thermal/Chemical Process 113

7.3 Kiln Injection 113

8 Case Study 114

9 Summary 114

Acronyms 114

References 115

3 Biosolids Thickening-Dewatering and Septage Treatment Nazih K Shammas, Azni Idris, Katayon Saed, Yung-Tse Hung, and Lawrence K Wang 121

1 Introduction 122

2 Expressor Press 123

3 Som-A-System 125

4 CentriPress 127

5 Hollin Iron Works Screw Press 128

6 Sun Sludge System 132

7 Wedgewater Bed 134

8 Vacuum-Assisted Bed 136

9 Reed Bed 137

10 Sludge-Freezing Bed 139

11 Biological Flotation 140

12 Septage Treatment 140

12.1 Receiving Station (Dumping Station/Storage Facilities) 140

12.2 Receiving Station (Dumping Station, Pretreatment, Equalization) 141

12.3 Land Application of Septage 142

12.4 Lagoon Disposal 144

12.5 Composting 145

12.6 Odor Control 146

References 147

4 Waste Chlorination and Stabilization Lawrence K Wang 151

1 Introduction 151

1.1 Process Introduction 151

1.2 Glossary 152

2 Wastewater Chlorination 153

2.1 Process Description 153

2.2 Design and Operation Considerations 154

2.3 Process Equipment and Control 157

2.4 Design Example—Design of a Wastewater Chlorine Contact Chamber 158

2.5 Application Example—Coxsackie Sewage Treatment Plant, Coxsackie, NY, USA 165

3 Sludge Chlorination and Stabilization 167

3.1 Process Description 167

3.2 Design and Operation Considerations 169

3.3 Process Equipment and Control 171

3.4 Application Example—Coxsackie Sewage Treatment Plant, Coxsackie, NY, USA 178

4 Septage Chlorination and Stabilization 183

4.1 Process Description 183

4.2 Design and Operation Considerations 184

4.3 Process Equipment and Control 186

4.4 Design Criteria 186

5 Safety Considerations of Chlorination Processes 187

6 Recent Advances in Waste Disinfection 188

Nomenclature 189

Acknowledgments 189

References 190

5 Storage of Sewage Sludge and Biosolids Nazih K Shammas and Lawrence K Wang 193

1 Introduction 193

1.1 Need for Storage 194

1.2 Risks and Benefits of Solids Storage Within Wastewater Treatment Systems 194

1.3 Storage Within Wastewater Sludge Treatment Processes 194

1.4 Field Storage of Biosolids 195

1.5 Effects of Storage on Wastewater Solids 195

1.6 Types of Storage 196

2 Wastewater Treatment Storage 197

2.1 Storage Within Wastewater Treatment Processes 197

2.2 Storage Within Wastewater Sludge Treatment Processes 206

3 Facilities Dedicated to Storage of Liquid Sludge 208

3.1 Holding Tanks 208

3.2 Facultative Sludge Lagoons 213

3.3 Anaerobic Liquid Sludge Lagoons 229

3.4 Aerated Storage Basins 232

4 Facilities Dedicated to Storage of Dewatered Sludge 233

4.1 Drying Sludge Lagoons 234

4.2 Confined Hoppers or Bins 237

4.3 Unconfined Stockpiles 241

5 Field Storage of Biosolids 242

5.1 Management of Storage 243

5.2 Odors 245

5.3 Water Quality 250

5.4 Pathogens 255

6 Design Examples 261

Nomenclature 267

References 267

Appendix 272

6 Regulations and Costs of Biosolids Disposal and Reuse Nazih K Shammas and Lawrence K Wang 273

1 Introduction 274

1.1 Historical Background 274

1.2 Background of the Part 503 Rule 275

1.3 Risk Assessment Basis of the Part 503 Rule 276

1.4 Overview of the Rule 276

2 Land Application of Biosolids 277

2.1 Pollutant Limits, and Pathogen and Vector Attraction Reduction Requirements 280

2.2 Options for Meeting Land Application Requirements 280

2.3 General Requirements and Management Practices 290

2.4 Frequency of Monitoring Requirements 292

2.5 Record-Keeping and Reporting Requirements 292

2.6 Domestic Septage 293

2.7 Liability Issues and Enforcement Oversight 293

3 Surface Disposal of Biosolids 294

3.1 General Requirements for Surface Disposal Sites 295

3.2 Pollutant Limits for Biosolids Placed on Surface Disposal Sites 296

3.3 Management Practices for Surface Disposal of Biosolids 297

3.4 Pathogen and Vector Attraction Reduction Requirements for Surface Disposal Sites 302

3.5 Frequency of Monitoring Requirements for Surface Disposal Sites 303

3.6 Record-Keeping and Reporting Requirements for Surface Disposal Sites 305

3.7 Regulatory Requirements for Surface Disposal of Domestic Septage 305

4 Incineration of Biosolids 305

4.1 Pollutant Limits for Biosolids Fired in a Biosolids Incinerator 306

4.2 Total Hydrocarbons 314

4.3 Management Practices for Biosolids Incineration 316

4.4 Frequency of Monitoring Requirements for Biosolids Incineration 317

4.5 Record-Keeping and Reporting Requirements for Biosolids Incineration 320

5 Pathogen and Vector Attraction Reduction Requirements 320

5.1 Pathogen Reduction Alternatives 320

5.2 Requirements for Reducing Vector Attraction 328

6 Costs 332

6.1 Description of Alternatives 333

6.2 Cost Relationships 336

6.3 Sludge Disposal Cost Curves 336

6.4 Procedure for Using the Diagram 337

Nomenclature 338

References 338

Appendix 342

7 Engineering and Management of Agricultural Land Application Lawrence K Wang, Nazih K Shammas, and Gregory Evanylo 343

1 Introduction 344

1.1 Biosolids 344

1.2 Biosolids Production and Pretreatment Before Land Application 344

1.3 Biosolids Characteristics 345

1.4 Agricultural Land Application for Beneficial Use 347

1.5 U.S Federal and State Regulations 348

2 Agricultural Land Application 353

2.1 Land Application Process 353

2.2 Agricultural Land Application Concepts and Terminologies 355

3 Planning and Management of Agricultural Land Application 361

3.1 Planning 361

3.2 Nutrient Management 361

4 Design of Land Application Process 364

4.1 Biosolids Application Rate Scenario 364

4.2 Step-by-Step Procedures for Biosolids Application Rate Determination 366

4.3 Simplified Sludge Application Rate Determination 372

5 Operation and Maintenance 373

5.1 Operation and Maintenance Process Considerations 373

5.2 Process Control Considerations 373

5.3 Maintenance Requirements and Safety Issues 373

6 Normal Operating Procedures 374

6.1 Startup Procedures 374

6.2 Routine Land Application Procedures 374

6.3 Shutdown Procedures 374

7 Emergency Operating Procedures 374

7.1 Loss of Power or Fuel 374

7.2 Loss of Other Biosolids Treatment Units 374

8 Environmental Impacts 375

9 Land Application Costs 376

10 Practical Applications and Design Examples 376

10.1 Biosolids Pretreatment Before Agricultural Land Application 376

10.2 Advantages and Disadvantages of Biosolids Land Application 377

10.3 Design Worksheet for Determining the Agronomic Rate 378

10.4 Calculation for Available Mineralized Organic Nitrogen 378

10.5 Risk Assessment Approach Versus Alternative Regulatory Approach to Land Application of Biosolids 378

10.6 Tracking Cumulative Pollutant Loading Rates on Land Application Sites 383

10.7 Management of Nitrogen in the Soils and Biosolids 383

10.8 Converting Dry Tons of Biosolids per Acre to Pound of Nutrient per Acre 386

10.9 Converting Percent Content to Pound per Dry Ton 387

10.10 Calculating Net Primary Nutrient Crop Need 387

10.11 Calculating the Components of Plant Available Nitrogen in Biosolids 388

10.12 Calculating the First Year PAN 0 – 1 from Biosolids 389

10.13 Calculating Biosolids Carryover Plant Available Nitrogen 390

10.14 Calculating Nitrogen-Based Agronomic Rate 391

10.15 Calculating the Required Land for Biosolids Application 394

10.16 Calculating the Nitrogen-Based and the Phosphorus-Based Agronomic Rates for Agricultural Land Application 394

10.17 Calculating the Lime-Based Agronomic Rate for Agricultural Land Application 396

10.18 Calculating Potassium Fertilizer Needs 397

10.19 Biosolids Land Application Costs and Cost Adjustment 398

11 Glossary of Land Application Terms 400

Nomenclature 404

References 406

Appendix A 410

Appendix B 412

Appendix C 413

8 Landfilling Engineering and Management Puangrat Kajitvichyanukul, Jirapat Ananpattarachai, Omotayo S Amuda, Abbas O Alade, Yung-Tse Hung, and Lawrence K Wang 415

1 Introduction 415

2 Regulations and Pollutant Standards for Biosolids Landfilling 416

3 Types of Biosolids for Landfilling 419

4 Requirements of Biosolids Characteristics for Landfilling 421

4.1 Class A Pathogen Requirements 421

4.2 Class B Pathogen Requirements 423

4.3 Other Biosolids Characteristics for Landfilling 423

4.4 Analytical Methods in Determining Biosolids Characteristics 427

5 Biosolids Treatment for Landfilling 427

5.1 Conditioning 428

5.2 Thickening 428

5.3 Stabilization 429

5.4 Dewatering 431

6 Design of Biosolids Landfilling 432

6.1 Landfilling Application for Biosolids 432

6.2 Biosolids Monofill 433

6.3 Design Criteria 436

7 Case Study and Example 438

7.1 Future Trends in Biosolids Landfilling 438

7.2 Calculation Examples 439

References 441

9 Ocean Disposal Technology and Assessment Kok-Leng Tay, James Osborne and Lawrence K Wang 443

1 Introduction 444

2 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter—London Convention 1972 446

3 Waste Assessment Guidance 446

4 Waste Assessment Audit 447

5 Waste Characterization Process and Disposal Permit System 449

5.1 Assessment of Material for Disposal 449

5.2 Chemical Screening 450

5.3 Biological Testing 451

5.4 Ecological and Human Health Risk Assessment 454

5.5 Water Quality Issues 457

6 Disposal Site Selection 457

7 Disposal Site Monitoring 458

7.1 Acoustic Geophysical Surveys 459

7.2 Currents and Sediment Transport Survey 460

7.3 Chemical and Biological Sampling 460

7.4 Case Studies 461

8 Land-Based Discharges of Wastes to the Sea: Engineering Design Considerations 463

8.1 Ocean Outfall System 464

8.2 Initial Dilution 466

8.3 Dispersion Dilution 466

8.4 Decay Dilution 466

8.5 Outfall Design Criteria 467

8.6 Design Example 468

9 Marine Pollution Prevention (The City of Los Angeles Biosolids Environmental Management System) 469

10 Ocean Disposal Technology Assessment and Conclusions 471

Nomenclature 472

References 473

10 Combustion and Incineration Engineering Walter R Niessen 479

1 Introduction to Incineration 479

2 Process Analysis of Incineration Systems 480

2.1 Stoichiometry 480

2.2 Thermal Decomposition (Pyrolysis) 494

2.3 Mass Burning 499

2.4 Suspension Burning 502

2.5 Air Pollution from Incineration 502

2.6 Fluid Mechanics in Furnace Systems 510

3 Incineration Systems for Municipal Solid Waste 515

3.1 Receipt and Storage 519

3.2 Charging 520

3.3 Enclosures 522

3.4 Grates and Hearths 524

3.5 Combustion Air 530

3.6 Flue Gas Conditioning 531

3.7 Air Pollution Control 533

3.8 Special Topics 538

4 Thermal Processing Systems for Biosolids 560

4.1 Introduction 560

4.2 Objectives and General Approach 562

4.3 Low-Range (Ambient, 100 ◦C) Drying Processes 566

4.4 Mid-Range (250 ◦to 1000◦C or 300◦to 1800◦F) Combustion Processes 576

4.5 High-Range (>1100◦C or>2000◦F) Combustion Processes 588

4.6 Discussion 589

5 Economics of Incineration 590

5.1 General 592

5.2 Capital Investment 594

5.3 Operating Costs 594

6 An Approach to Design 594

6.1 Characterize the Waste 594

6.2 Lay Out the System in Blocks 597

6.3 Establish Performance Objectives 597

6.4 Develop Heat and Material Balances 597

6.5 Develop Incinerator Envelope 597

6.6 Evaluate Incinerator Dynamics 599

6.7 Develop the Design of Auxiliary Equipment 599

6.8 Review Heat and Material Balances 599

6.9 Build and Operate 599

Appendix: Waste Thermochemical Data 599

A.1 Refuse Composition 600

A.2 Solid Waste Properties 601

A.3 Ash Composition 601

References 602

11 Combustion and Incineration Management Mingming Lu and Yu-Ming Zheng 607

1 Introduction 607

1.1 Overview of Biosolids Incineration 607

1.2 Overview of the Dewatering Process 608

1.3 Overview of Air Pollution Control Devices 609

1.4 Overview of the Ash-Handling System 611

1.5 U.S Federal and State Regulations 613

2 Operation and Management of the Multiple Hearth Furnace 621

2.1 Process Description 621

2.2 Design and Operating Parameters 623

2.3 Performance Evaluation, Management, and Troubleshooting of the Multiple Hearth Furnace 626

3 Operation and Management of the Fluidized Bed Furnace 633

3.1 Process Description 633

3.2 Design and Operating Parameters 634

3.3 Performance Evaluation, Management, and Troubleshooting of the Fluidized Bed Furnace 635

3.4 Fluidized Bed Incinerator with Improved Design 637

3.5 Comparison Between Multiple Hearth and Fluidized Bed Furnaces 639

4 Other Incineration Processes 640

4.1 Electric Infrared Incinerators 640

4.2 Co-Incineration 640

4.3 Other Sludge Incineration Techniques 643

Nomenclature 644

References 644

12 Beneficial Utilization of Biosolids Nazih K Shammas and Lawrence K Wang 647

1 Introduction 647

2 Federal Biosolids Regulations 649

2.1 Background 649

2.2 Risk Assessment Basis of Part 503 650

2.3 Overview of Part 503 651

2.4 Requirements for Land Application 651

2.5 Requirements for Biosolids Placed on a Surface Disposal Site 653

2.6 Requirements for Pathogen and Vector Attraction Reduction 653

2.7 Requirements for Biosolids Fired in Incinerators 653

2.8 Enforcement of Part 503 and Reporting Requirements 655

2.9 Relationship of the Federal Requirements to State Requirements 655

3 Land Application of Biosolids 656

3.1 Perspective 656

3.2 Principles and Design Criteria 658

3.3 Options for Meeting Land Application Requirements 659

3.4 Site Restrictions, General Requirements, and Management Practices 668

3.5 Process Design 668

3.6 Facilities Design 669

3.7 Facility Management, Operations, and Monitoring 670

4 Surface Disposal of Biosolids 670

4.1 Perspective 670

4.2 Differentiation Among Surface Disposal, Storage, and Land Application 671

4.3 Pollutant Limits for Biosolids 671

4.4 Pathogens and Vector Attraction Reduction Requirements 672

4.5 Frequency of Monitoring Requirements 673

4.6 Regulatory Requirements for Surface Disposal of Domestic Septage 674

5 Incineration of Biosolids as an Energy Source 675

5.1 Perspective 675

5.2 Recovery of Energy from Biosolids 676

5.3 Factors Affecting Heat Recovery 679

5.4 Pollutant Limits for Biosolids Fired in Incinerators 680

6 Other Uses of Wastewater Solids and Solid By-Products 684

7 Examples 685

7.1 Example 1: Determination of the Annual Whole Sludge (Biosolids) Application Rate (AWSAR) 685

7.2 Example 2: Determination of the Amount of Nitrogen Provided by the AWSAR Relative to the Agronomic Rate 685

Nomenclature 686

References 687

13 Process Selection of Biosolids Management Systems Nazih K Shammas and Lawrence K Wang 691

1 Introduction 691

2 The Logic of Process Selection 692

2.1 Identification of Relevant Criteria 693

2.2 Identification of System Options 693

2.3 System Selection Procedure 693

2.4 Parallel Elements 701

2.5 Example of Process Selection at Eugene, Oregon 704

3 Sizing of Equipment 707

4 Approaches to Sidestream Management 710

4.1 Sidestream Production 710

4.2 Sidestream Quality and Potential Problems 711

4.3 General Approaches to Sidestream Problems 712

4.4 Elimination of Sidestream 712

4.5 Modification of Upstream Solids Processing Steps 712

4.6 Change in Timing, Return Rate, or Return Point 713

4.7 Modification of Wastewater Treatment Facilities 714

4.8 Separate Treatment of Sidestreams 715

5 Contingency Planning 721

5.1 Contingency Problems and Their Solutions 721

5.2 Example of Contingency Planning for Breakdowns 722

6 Site Variations 725

7 Energy Conservation 725

8 Cost-Effective Analyses 726

9 Checklists 727

10 U.S Practices in Managing Biosolids 729

10.1 Primary Biosolids Processing Trains 729

10.2 Secondary Biosolids Processing Trains 734

10.3 Combined Biosolids Processing Trains 735

10.4 Types of Unit Processes 737

References 739

Appendix: Conversion Factors for Environmental Engineers Lawrence K Wang 745

Index 789

ABBASO ALADE,MSc • Assistant Lecturer, Department of Chemical Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria

OMOTAYO S AMUDA, PhD • Senior Lecturer, Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomoso, Nigeria

JIRAPAT ANANPATTARACHAI, MSc • Researcher, Department of tal Engineering, King Mongkut’s University of Technology Thonburi, Bangkok Thailand

Environmen-ANDENG,PhD • Associate Professor, College of Civil Engineering, Hohai University, Nanjing, China

GREGORYEVANYLO,PhD • Professor and Extension Specialist, Crop and Soil ronmental Sciences, Virginia Tech, Blacksburg, VA

Envi-YUNG-TSEHUNG,PhD,PE,DEE • Professor, Department of Civil and Environmental Engineering, Cleveland State University, Cleveland, OH

AZNIIDRIS,PhD • Professor, Department of Chemical & Environmental Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia

PUANGRAT KAJITVICHYANUKUL, PhD • Associate Professor, Department of ronmental Engineering, Mongkut’s University of Technology Thonburi, Bangkok Thailand

Envi-MINGMING LU, PhD • Associate Professor, Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, OH

WALTERR NIESSEN,MSc,PE,DEE • President, Niessen Consultants, S P., Andover, MA

JAMES OSBORNE, BS • Senior Manager, Jim Osborne Environmental Consultants, Chelsea, Quebec, Canada

KATAYON SAED, PhD • Assistant Professor, Department of Civil Engineering, versiti Putra Malaysia, Serdang, Selangor, Malaysia

Uni-NAZIH K SHAMMAS, PhD • Professor, Ex-Dean and Director, Lenox Institute of Water Technology, Lenox, MA; Advisor, Krofta Engineering Corporation, Lenox, MA; Environmental Engineering Consultant

KOK-LENG TAY, PhD • Head, Contaminated Sites and Wastes Management Unit, Environment Canada, Atlantic Region, Dartmouth, Nova Scotia, Canada

LAWRENCE K WANG, PhD,PE,DEE • Dean and Director (retired), Lenox Institute

of Water Technology, Lenox, MA; Assistant to the President (retired), Krofta neering Corporation, Lenox, MA; and Vice President (retired), Zorex Corporation, Newtonville, NY

Engi-YU-MING ZHENG, PhD • Research Fellow, Division of Environmental Science & Engineering, National University of Singapore, Singapore

xxi

Transport and Pumping of Sewage

Sludge and Biosolids

Nazih K Shammas and Lawrence K Wang

C ONTENTS

INTRODUCTION

PUMPING

PIPELINES

DEWATEREDWASTEWATERSOLIDSCONVEYANCE

LONG-DISTANCEWASTEWATERSOLIDSHAULING

POTENTIALRISK TOBIOSOLIDSEXPOSURE

Key Words Sewage sludge rbiosolids rtransport rpumping rpipelines rheadloss r

conveyorsrhaulingrtrucksrtrainsrbargesrrisk to exposure.

1 INTRODUCTION

1.1 Sewage Sludge and Biosolids

Solids removed by wastewater treatment processes include screenings and grit, urally floating materials called scum, and the removed solids from primary and sec-

nat-ondary clarifiers called sewage sludge The term biosolids is the new name for what

had previously been referred to as stabilized sewage sludge Biosolids are primarily

From: Handbook of Environmental Engineering, Volume 7: Biosolids Engineering and Management

Edited by: L K Wang, N K Shammas and Y T Hung c
The Humana Press, Totowa, NJ

1

organic treated wastewater residues from municipal wastewater treatment plants—with

the emphasis on the word treated—that are suitable for recycling as a soil amendment Sewage sludge is now the term used to refer to untreated primary and secondary organic

solids This usage of terminology differentiates between biosolids, which refer to theorganic solids that have received stabilization treatment at a municipal wastewatertreatment plant, and the many other types of sludges (such as industrial oil and gas fieldwastes) that cannot be beneficially recycled as soil amendment

1.2 Biosolids Applications

Biosolids can be used as a slow release nitrogen fertilizer with low concentrations

of other plant nutrients In addition to significant amounts of nitrogen, biosolids alsocontain phosphorus, potassium, and essential micronutrients such as zinc and iron Manysoils in the western United States are deficient in micronutrients Biosolids are rich inorganic matter that can improve soil quality by improving water-holding capacity, soilstructure, and air and water transport Proper use of biosolids can ultimately decreasetopsoil erosion

Moreover, biosolids may provide an economic benefit in addition to their mental advantages Continuous application of three dry tons per acre every other year todry land planted with wheat may produce comparable yields, higher protein content,and larger economic returns compared with the use of 50 to 60 pounds per acre ofcommercial nitrogen fertilizer

environ-1.3 Transport and Pumping of Sewage Sludge and Biosolids

The fundamental objective of all wastewater treatment operations is to remove sirable constituents present in wastewater and consolidate these materials for furtherprocessing, utilization, or disposal This chapter discusses the transportation of solidsremoved by the wastewater treatment processes or the movement of scum, sewagesludge, biosolids, or other miscellaneous solids from point to point for treatment, storage,utilization, or disposal Transportation includes movement of solids by pumping andpipelines, conveyors, or hauling equipment

Unless biosolids have been dewatered, they can be transported most efficiently andeconomically by pumping through pipelines Biosolids are subject to the same physicallaws as other fluids Simply stated, work put into a fluid by a pump alters velocity,elevation, and pressure, and overcomes friction loss The unique flow characteristics

of biosolids create special problems and constraints Nevertheless, biosolids have beensuccessfully pumped through short pipelines at up to 20% solids by weight, as well as inpipelines of over 10 miles (16 km) long at up to 8% solids concentrations (1)

Fig 1.1 Centrifugal pump Source: US EPA (1).

2.1 Types of Sludge and Biosolids Pumps

Wastewater sludge and biosolids can range in consistency from a watery scum tothick paste-like slurry A different type of pump may be required for each type ofsolids Pumps that are currently utilized for sludge and biosolids transport includecentrifugal, torque flow, plunger, piston, piston/hydraulic diaphragm, progressive cavity,rotary, diaphragm, ejector, and air lift types Water eductor pumps are sometimes used

to pump grit from aerated grit removal tanks

2.1.1 Centrifugal Pumps

A centrifugal pump (Figure 1.1) consists of a set of rotating vanes in a housing

or casing The vanes may be either open or enclosed The vanes impart energy to

a fluid through centrifugal force The nonclog centrifugal pump for wastewater orbiosolids, in comparison to a centrifugal pump designed to handle clean water, hasfewer but larger and less obstructed vane passageways in the impeller; has greaterclearances between impeller and casing; and has sturdier bearings, shafts, and seals.Such nonclog centrifugal pumps may be used to circulate digester contents and transfersludges with lower solids concentrations, such as waste activated sludge The largerpassageways and greater clearances result in increased reliability at a cost of lowerefficiency

The basic problem with using any form of centrifugal pump on sludge/biosolids ischoosing the correct size At any given speed, centrifugal pumps operate well only if thepumping head is within a relatively narrow range; the variable nature of sludge/biosolids,however, causes pumping heads to vary The selected pumps must be large enough topass solids without clogging of the impellers and yet small enough to avoid the problem

of diluting the sludge/biosolids by drawing in large quantities of overlying wastewater.Throttling the discharge to reduce the capacity of a centrifugal pump is impractical bothbecause of energy inefficiency and because frequent clogging of the throttling valvewill occur It is recommended that centrifugal pumps requiring capacity adjustment be

equipped with variable-speed drives Fixed capacity in multiple pump applications isachieved by equipping each pump with a discharge flow meter and using the flow metersignal in conjunction with the variable speed drive to control the speed of the pump.Seals last longer if back suction pumps are used Utilizing the back of the impeller forsuction removes areas of high pressure inside the pump casing from the location of theseal and prolongs seal life.

Propeller or mixed flow centrifugal pumps are sometimes used for low head cations because of higher efficiencies; a typical application is return activated sludgepumping When being considered for this type of application, such pumps must be ofsufficient size (usually at least 12 inches (in) [300 mm] in suction diameter) to provideinternal clearances capable of passing the type of debris normally found within theactivated sludge system Such pumps should not be used in activated sludge systemsthat are not preceded with primary sedimentation facilities

appli-2.1.2 Torque Flow Pumps

A torque flow pump (Figure 1.2), also known as a recessed impeller or vortex pump,

is a centrifugal pump in which the impeller is open faced and recessed well back into thepump casing The size of particles that can be handled by this type of pump is limitedonly by the diameter of the suction or discharge openings The rotating impeller imparts

a spiraling motion to the fluid passing through the pump Most of the fluid does notactually pass through the vanes of the impeller, thereby minimizing abrasive contactwith it and reducing the chance of clogging Because there are no close tolerancesbetween the impeller and casing, the chances for abrasive wear within the pump arefurther reduced The price paid for increased pump longevity and reliability is that thepumps are relatively inefficient compared with other nonclog centrifugals; 45% versus65% efficiency is typical Torque flow pumps for sludge/biosolids service should always

Fig 1.2 Torque flow pump Source: US EPA (1).

DESURGING CHAMBER

DESURGING CHAMBER PACKING

SUCTION

BALL CHECK

CYLINDER WALL PISTON

Fig 1.3 Plunger pump Source: US EPA (1).

have nickel or chrome abrasion-resistant volute and impellers The pumps must be sizedaccurately so that excessive recirculation does not occur at any condition at operatinghead Capacity adjustment and control is achieved in the same manner as for othercentrifugal pumps

2.1.3 Plunger Pumps

Plunger pumps (Figure 1.3) consist of pistons driven by an exposed drive crank.The eccentricity of the drive crank is adjustable, offering a variable stroke length andhence a variable positive displacement pumping action The check valves, ball or flap,are usually paired in tandem before and after the pump Plunger pumps have constantcapacity regardless of large variations in pumping head, and can handle sludges up to15% solids if designed specifically for such service Plunger pumps are cost-effectivewhere the installation requirements do not exceed 500 gallons per minute (gpm) (32 L/s),

a 200 ft (61 m) discharge head, or 15% sludge solids (1) Plunger pumps require dailyroutine servicing by the operator, but overhaul maintenance effort and cost are low.The plunger pump’s internal mechanism is visible The pump’s connecting rodattaches to the piston inside its hollow interior, and this “bowl” is filled with oil forlubrication of the journal bearing Either the piston exterior or the cylinder interiorhouses the packing, which must be kept moist at all times Water for this purpose isusually supplied from an annular pool located above the packing; the pool receives aconstant trickle of clean water If the packing fails, sludge may be sprayed over thesurrounding area

Plunger pumps may operate with up to 10 ft (3 m) of suction lift; however, suctionlifts may reduce the solids concentration that can be pumped The use of the pump withthe suction pressure higher than the discharge is not practical because flow will be forcedpast the check valves The use of special intake and discharge air chambers reduces noiseand vibration These chambers also smooth out pulsations of intermittent flow Pulsationdampening air chambers, if used, should be glass lined to avoid destruction by hydrogen

Fig 1.4 Piston pump Source: US EPA (1).

sulfide corrosion If the pump is operated when the discharge pipeline is obstructed,serious damage may occur to the pump, motor, or pipeline; this problem can be avoided

by a simple shear pin arrangement

2.1.4 Piston Pumps

Piston pumps are similar in action to the plunger pumps, but consist of a guide pistonand a fluid power piston (Figure 1.4) Piston pumps are capable of generating highpressures at low flows These pumps are more expensive than other types of positivedisplacement sludge pumps and are usually used in special applications such as feedpumps for heat treatment systems As with other types of positive displacement pumps,shear pins or other devices must be used to prevent damage due to obstructed pipelines

A variation of the piston pump has been developed for use where reliability andclose control are needed The pump utilizes a fluid power piston driving an intermediatehydraulic fluid (clean water), which in turn pumps the sludge/biosolids in a diaphragmchamber (Figure 1.5) The speed of the hydraulic fluid drive piston can be controlled toprovide pump discharge conditions ranging from constant flow rate to constant pressure.This pump is used primarily as a feed pump for filter presses This special pump has the

Fig 1.5 Combination piston-hydraulic diaphragm pump Source: US EPA (1).

Fig 1.6 Progressive cavity pump Source: US EPA (1).

greatest initial cost of any piston pump, but the cost is usually offset by low maintenanceand high reliability

2.1.5 Progressive Cavity Pumps

The progressive cavity pump (Figure 1.6) has been used successfully on almost alltypes of sludge/biosolids This pump comprises a single-threaded rotor that operates with

an interference clearance in a double-threaded helix stator made of rubber A volume or

“cavity” moves “progressively” from suction to discharge when the rotor is rotating,hence the name “progressive cavity.” The progressive cavity pump may be operated

at discharge heads of 450 ft (137 m) on sludge/biosolids Capacities are available to

1200 gpm (75 L/s) Some progressive cavity pumps will pass solids up to 1.125 in(2.9 cm) in diameter Rags or stringy material should be ground up before entering thispump The rotor is inherently self-locking in the stator housing when not in operation,and acts as a check valve for the sludge/biosolids pumping line An auxiliary motor brakemay be specified to enhance this operational feature

The total head produced by the progressive cavity pump is divided equally betweenthe number of cavities created by the threaded rotor and helix stator The differentialpressure between cavities directly relates to the wear of the rotor and stator because of theslight “blow by” caused by this pressure difference Because wear on the rotor and stator

is high, the maintenance cost for this type of pump is the highest of any sludge/biosolidspump Maintenance costs are reduced by specifying the pump for one class higherpressure service (one extra stage) than would be used for clean fluids This createsmany extra cavities, reduces the differential pressure between cavities, and consequentlyreduces rotor and stator wear Also, speeds should not exceed 325 revolutions per minute(rpm) in sludge/biosolids service, and grit concentrations should be minimized

Since the rotor shaft has an eccentric motion, universal joints are required between themotor shaft and the rotor The design of the universal joint varies greatly among differentmanufacturers Continuous duty, trouble-free operation of these universal joints is bestachieved by using the best quality (and usually most expensive) universal gear jointdesign Discharge pressure safety shutdown devices are required on the pump discharge

to prevent rupture of blocked discharge lines No-flow safety shutdown devices are oftenused to prevent the rotor and stator from becoming fused due to dry operation Aspreviously mentioned, these pumps are expensive to maintain However, flow rates areeasily controlled, pulsation is minimal, and operation is clean Therefore, progressivecavity pumps are widely used for pumping sludge/biosolids

2.1.6 Diaphragm Pumps

Diaphragm pumps (Figure 1.7) utilize a flexible membrane that is pushed or pulled

to contract or enlarge an enclosed cavity Flow is directed through this cavity by checkvalves, which may be either ball or flap type The capacity of a diaphragm pump isaltered by changing either the length of the diaphragm stroke or the number of strokesper minute Pump capacity can be increased and flow pulsations smoothed out byproviding two pump-chambers and utilizing both strokes of the diaphragm for pumping.Diaphragm pumps are relatively low-head and low-capacity units; the largest availableair-operated diaphragm pump delivers 220 gpm (14 L/s) against 50 ft (15 m) of head(1) The distinct advantage of the diaphragm pumps is their simplicity Their needsfor operator attention and maintenance are minimal There are no seals, shafts, rotors,stators, or packing in contact with the fluid; also, diaphragm pumps can run in a drycondition indefinitely

Flexure of the diaphragm may be accomplished mechanically (push rod or spring)

or hydraulically (air or water) Diaphragm life is more a function of the discharge headand the total number of flexures than the abrasiveness or viscosity of the pumped fluid.Power to drive air driven diaphragm pumps is typically double that required to operate

a mechanically driven pump of similar capacity However, hydraulically operated (air or

Fig 1.7 Diaphragm pump Source: US EPA (1).

water) diaphragms generally outwear mechanically driven diaphragms by a considerableamount Hydraulically driven diaphragm pumps are suitable for operation in hazardousexplosion-prone areas; also a pressure release means in the hydraulic system providesprotection against obstructed pipelines Typical repairs to a diaphragm pump usually costless than USD 172 (2007 basis) for parts and require approximately 2 hours of labor (1)

In some locations, high humidity intake air causes icing problems to develop at the airrelease valve and muffler on an air-driven diaphragm pump A compressed air dryershould be used in the air supply system when such a condition exists

The overall construction of some diaphragm pumps, the common “trash pump,” issuch that abrasion may cause the lightweight casings to fail before the diaphragms,since the pumps are not designed for continuous service For wastewater treatmentapplications, the mechanical diaphragm “walking beam” pumps are more appropriate.These pumps are dependable, have quick cleanout ball or flap check valves, and arepresently used to handle scum and sludge at numerous small plants throughout thecountry

One air-driven diaphragm pump is sold in a package expressly intended for ing sludge from primary sedimentation tanks and gravity thickeners The basic pumppackage consists of a single-chambered, spring return diaphragm pump, an air pressureregulator, a solenoid valve, a gauge, a muffler, and an electronic transistorized timer.This unit pumps a single 3.8-gallon (14.4-L) stroke after an interval of time The interval

pump-is readily adjusted to match the pumping rate to the rate of formation of the sludgeblanket in the sedimentation tank or thickener The large single stroke capacity of this

pump has several maintenance advantages Not only is total flexure count reduced, butball valve flushing is improved, so large particles cause less difficulty The maximumrecommended solids size is 7/8 in (2.2 cm) Pump stroke speed is constant regardless ofthe selected pump flow so that minimum scouring velocities are always maintained inthe discharge piping during the pumping surge.

The traditional sequence of intermittent pumping for primary sedimentation tankshas been to thicken for an interval without pumping and then draw the sludge blanketdown A relatively long interval is required by pump motors, since frequent motor startscan cause overheating Theoretically, if the sludge concentration is 10% on the bottomand decreases to 8% at the top of the pumped sludge zone, then the pumped average

is 9% However, by using air drive, a diaphragm pump can operate with starts everyfew seconds instead of every several minutes or longer The manufacturer claims itssystem will draw single intermittent pulses from the 10% bottom layer since the sludgeblanket depth is maintained at a virtually constant height Downstream sludge treatmentprocesses can have greater solids capacity because more concentrated sludges can beobtained

The City of San Francisco ran independent pump evaluation tests (2) and concludedthat proper use of air-driven diaphragm pumps increases the sedimentation tanks’ ability

to concentrate sludges The sludge collection system in the sedimentation tanks andthe sludge pumping equipment had to be controlled together to give optimum thick-ening Savings in operations and maintenance as well as improved thickening wereaccomplished by lowering the overall average rate of sludge withdrawal and makingthe sludge collectors work continuously at a reduced rate instead of intermittently Whenconsidering such a pump installation, the capacity requirement is based on the maximumrate at which the sludge blanket forms in the tank and not the capacity required tomaintain minimum pipe velocities

2.1.7 Rotary Pumps

Rotary pumps (Figure 1.8) are positive displacement pumps in which two rotatingsynchronous lobes essentially push the fluid through the pump Because rotary pumplobe configurations can be designed for a specific application, rotary pumps are suitablefor jobs ranging from air compressor duty to wastewater sludge/biosolids pumping.Rotational speed and shearing stresses are low Wastewater pumping lobes are non-contact and clearances are factory changed according to the abrasive content of theslurry It is not recommended that the pumps be considered self-priming or suctionlift pumps, although they are advertised as such Experience at one plant indicatesthat the pump operates best with a bottom suction and top discharge Only very lim-ited operational data are available for rotary pumps used on sludge/biosolids Severalmanufacturers advertise hard metal two-lobed pumps for sludge/biosolids usage Lobereplacement for these pumps appears to be less costly than rotor and stator replace-ment on progressive cavity pumps Some manufacturers are offering hard rubber three-lobed rotary pumps, which are used successfully for sludge/biosolids pumping Rotarypumps, like other positive displacement pumps, must be protected against pipelineobstructions

Fig 1.8 Rotary pump Source: US EPA (1).

Fig 1.9 Ejection pump Source: US EPA (1).

2.1.8 Ejector Pumps

Wastewater ejectors use a charging pot, which is intermittently discharged by pressed air supply (Figure 1.9) Ejectors are most applicable for incoming average flowrates less than 150 gpm (9 L/s) These pumps require a positive suction and usuallydischarge to a vented holding tank or basin Scum and sludge/biosolids can incapac-itate the standard mechanical or electronic probe-type level sensors offered by mostmanufacturers to sequence pot discharge; custom instrumentation may be necessary.Large flushing and cleanout connections should be provided If ejectors are to be used

com-to discharge sludge/biosolids com-to an anaerobic digester where the air could produce anexplosive mixture, special precautions should be taken to see that the units cannot bleedexcessive quantities of air into the digester Ejector pumps have been used in someinstallations to pump thickened waste-activated sludge produced by the dissolved-airflotation (DAF) process.

2.1.9 Gas Lift Pumps

Gas lift pumps use low-pressure gas released within a confined riser pipe with an opentop and bottom The released gas bubbles rise, dragging the liquid up and out of the riserpipe Air is commonly used, in which case the pump is called an air-lift pump

Air-lift pumps are used for return activated sludge and similar applications; gas-liftpumps using digester gas are used to circulate the contents of anaerobic digesters Themain advantage of these relatively inefficient pumps is the complete absence of movingparts Gas-lift sludge/biosolids pumps are usually limited to lifts of less than 10 ft Thecapacity of a lift pump can be varied by changing its buoyant gas supply Reliablegas-lift pumping requires the gas supply to be completely independent of outside flow

or pressure variables Gas-lift pumps with an external gas supply and circumferentialdiffuser can pass solids of a size equivalent to the internal diameter of the confiningriser pipe without clogging When the gas is supplied by a separate inserted pipe,the obstruction created negates this nonclog feature Gas-lift pumps, because of theirlow lifting capability, are very sensitive to suction and discharge head variations, and

to variations in the depth of buoyant gas release Special discharge heads are usuallyrequired to enhance the complete separation of diffused air once the discharge elevationhas been reached

2.1.10 Water Eductors

Water eductors use the suction force (vacuum) created when a high-pressure waterstream is passed through a streamlined confining tube (Venturi) Like the air-lift pump,water eductors have no moving parts When water is required to transport a solidmaterial, the water eductor becomes a very convenient pump Most water eductors withreasonable water demands cannot pump solids the size of a golf ball However, they havebeen successfully used to remove grit from aerated grit removal tanks and discharge thegrit into dewatering classifiers

2.2 Application and Performance Evaluation of Sludge

and Sludge/Biosolids Pumps

This section describes appropriate applications for the pumps and identifies somelimitations and constraints It covers screenings, grit, scum, sewage sludge, as well assludge/biosolids

Centrifugal pumps are used to handle large volumes of flow that have low solidscontent, and when precise control of the flow rate is not required Centrifugal pumpsoften are used to return activated sludge and waste unthickened solids from primaryand secondary treatment processes This pump also is used for recirculation of digestercontents (with less than 4% or 5% total suspended solids [TSS], and for scum andskimmings removal (3)

The most common types of positive displacement pumps used for sludge andsludge/biosolids include the plunger, rotary pump, and diaphragm pump The plungerpump is the most popular pump for handling high viscosity sludge/biosolids contain-ing large and abrasive materials Of the rotary positive displacement pumps, only theprogressing cavity pump has widespread use in pumping sludge/biosolids This pump isself-priming and delivers a smooth flow in contrast to the plunger-type pump Not only

is the rotary displacement pump able to handle very thick sludge/biosolids, but it alsomay be used to transport sludge cake; it can pump centrifuge and filter cakes having 15%

to 40% TSS When the progressing cavity pump is made of the right materials, it alsomay be used for handling chemical slurries The diaphragm-type pump may be used forthe same applications as a plunger pump, except that it has no problems with abrasion.This pump also may be used for handling strong or toxic chemicals when leakage of thechemicals is a major concern

There are two main types of sludge/biosolids grinding pumps The first type is a minuting device, which produces only enough head to pass solids through the grinderitself This unit is mostly used for comminuting thickened sludge/biosolids, scum, andscreenings that may cause clogging in dewatering systems The second type of pumpscombines both grinding of solids and pumping of the liquid and comminuted solids Theunit may be used to grind scum and screenings, handle sludge/sludge/biosolids flows,and break up relatively large trash particles

com-Table 1.1 lists various types of sludge/biosolids pumps, their capacities, and deliveredpressure (3) This table may be used as a general guide to evaluating the performance

of sludge/biosolids pumps at a treatment plant For a very precise evaluation, the actualoperating characteristics of the pump should be checked against manufacturers designdata for the pump Pumps cannot be expected to operate beyond their designed capacityand intended use

Suction conditions require special attention when pumping sludge/sludge/biosolids.When pumping water or other newtonian fluids, calculations, of net positive suctionhead (NPSH) can be used to determine permissible suction piping arrangements How-ever, sludge/biosolids are non-newtonian fluids, especially at high solids concentrations.This behavior may drastically reduce the available NPSH Consequently, long suctionpipelines should be avoided, and the sludge/biosolids pump should be several feet below

Table 1.1

Type, capacity, and delivered pressure of sludge/biosolids pumps

Delivered pressure (psi)

Rotary positive displacement (progressing cavity pump) up to 400 up to 500

Sludge grinding pumps (comminuting and pumping type) 25–300 —

Source: US EPA (3).

the liquid level in the tank from which the sludge is to be pumped If these conditionsare not met, a pump will not be able to handle sludge/biosolids at high concentrations.Special precautions are usually required to reliably pump screenings and grit Screen-ings should be ground up and pumped by pumps with the ability to pass large material.Torque flow pumps are ideal for this application Grit pumping requires special abrasionand nonclogging considerations Both screenings and grit pumps should be easy todisassemble with quick access to the volute and impeller.

Table 1.2 presents an application matrix that identifies the various types ofsludge/sludge/biosolids normally encountered in wastewater applications, and provides

a guide for the suitability of each type of pump in that service (1)

2.3 Control Considerations

To be effective, sludge/sludge/biosolids pumping systems must be flexible underdifferent plant operating conditions The overall piping, valves, and pumping systemmust be set up to allow bypassing and provide standby pumping capacity when prob-lems occur The most important control considerations that must be understood by theoperator are as follows (3):

1 The total quantity of sludge/sludge/biosolids per day to be handled

2 The rate at which solids build up and must be removed

Unless the system and the operator are prepared to handle grit and other solids duringtimes of heavy solids inflow, the operator may find all the sludge/biosolids lines pluggedand overloaded The operator also must be aware of the effects of overpumping andunderpumping from different unit operations For example, removing solids at too high

a rate results in thin sludge/biosolids and overpumping of the thickener

Sludge removal rates may depend on downstream operations such as dewatering andcombustion For these processes, a uniform rate of solids delivery is necessary On theother hand, sludge/biosolids flow is not so critical in downstream units like aerobic

or anaerobic digestion If a sludge/biosolids concentrator is used, time is needed toaccumulate the solids (known as a “solids inventory”) If the removal rate is higherthan the stocking rate of the inventory, then the solids concentration will be lowered.Whenever possible, the concentration of the withdrawn sludge/biosolids should be used

to determine the sludge/biosolids pumping rate

When multiple units are used, it is best to withdraw thickened sludge/biosolids fromtwo or more units at the same time using a multiple pump arrangement This practiceresults in much more uniform and highly concentrated sludge/biosolids than doublingthe pumping rate of a single unit Another way is to pump at a higher rate but for a muchshorter time

Sludge removal from an aerobic or anaerobic digester is more efficient when thepumping schedule is based on solids accumulation The pumping program should tend tounderpump the thickener or secondary settling tank so that a daily manual check on thesludge/biosolids inventory can be made, and the pumping schedule adjusted to removeany accumulated inventory

Table 1.3 shows the problems that could be encountered in the operation of sludge/biosolids pumps, their probable causes, and their solutions (3)

Thickened sludge

Secondary sludge (Biosolids) Miscellaneous

solids

Primary sludge

Digested sludge, percent

Lagooned sludge, percent

Pump type

Ground screenings Grit Scum Septage

Settled sludge

Thickened sludge

Trickling filter

1 - Use only under special circumstances

2 - Use with caution

3 - Suitable with limitations

4 - Suitable

5 - Best type to use

Source: US EPA (1).

Troubleshooting of pumps’ operational problems

head loss on suction side of pump.

1a Sludge dilutes as it breaks through sludge blanket if pump

is operating at too high a rate.

1a (1) Pump sludge more frequently.

(2) Reduce speed of pump.

2 Unwanted (dilute) flow

of sludge through pump.

2a Improper location of pump.

2b Ball valve too light or ball hung

up on trash accumulations.

2b Visual inspection.

2a Relocate pump.

2b Change the weight of the ball check to prevent it from lifting and allowing dilute sludge to flow through the pump.

discharge pressure.

air chambers are filled with air.

(2) Change ball checks and seating arrangement.

(3) Modify pumping rate.

4 Pump inefficiency at

high suction.

4a Air leakage through pump seals

or valve stem seals.

4a Pour water around seal and visibly inspect sealing check;

you may also hear the leak.

4a Check seating and seals on valves, valve covers, valve stems, and piston on plunger pump (repair or replace damaged and worn parts).

6a Run pump on a longer stroke at slower speed.

6b Improper clearance adjustment

on grinder pump.

cutters.

7 Excessive leakage around

seals on shafts and

plungers.

7a Excessive wear on shaft or cylinder.

mechanical seals with water-lubricated seals.

8 Progressive cavity pump

unable to transport

sludge.

8a Slippage occurring in pump due

to wear on stators and rotors.

8b Pump operating at excessive speeds.

300 rpm.

Source: US EPA (3).

3 PIPELINES

3.1 Pipe, Fittings, and Valves

Materials for wastewater solids pipelines include steel, cast and ductile iron, sioned concrete cylinder pipe, thermoplastic, fiberglass reinforced plastic, and others.Steel and iron are most common With steel or iron, external corrosion may occur inunprotected buried lines; corrosion may be adequately controlled under most conditions

preten-by coatings and, where needed, cathodic protection Inside the pipe, a lining of cement,plastic, or glass may be used to protect the pipe from internal corrosion and abrasion.With raw sludge and scum, linings have an additional function: they provide a smoothsurface that greatly retards accumulations of grease on the pipe wall (4, 5) Withanaerobically digested biosolids, linings may be useful to prevent crystals of struvitefrom growing on the pipe wall Smooth linings are especially valuable in pump suctionpiping and in key portions of piping (header pipes and the like) where maintenanceshutdowns would cause process difficulties

Fittings and appurtenances must be compatible with sludge/biosolids and pipe Longsweep elbows are preferred over short radius elbows Grit piping may be provided withelbows and tees made of special erosion-resistant materials Valves of the nonlubricatedeccentric plug type have proven reliable in sludge/biosolids pipeline service Care must

be taken if a cleaning tool is to pass through the valves Grit pipelines are usuallyequipped with tapered lubricated plug valves

Wastewater solids piping should be designed for reasonably convenient maintenance.Even under good conditions, pipe may occasionally have erosive wear, grease deposits,

or other difficulties Pipe in tunnels or galleries is more accessible than buried pipe

An adequate number of flanged joints, mechanical couplings, and takedown fittingsshould be provided It is recommended that 4 to 6 in (100 to 150 mm) be consideredthe minimum diameter for wastewater solids pipelines to minimize grease clogging

or particle blockage and facilitate maintenance Blind flanges and cleanouts should

be provided for ease of line maintenance Gas formation by wastewater solids left forlong periods in confined pipe or equipment can create explosive pressures; therefore,provision should be made for flushing and draining all pipes, pumps, and equipment Thepressure rating of wastewater solids pipelines should be adequate for unusual as well asroutine operating pressures Unusual pressures occasionally occur due to high solids con-centrations, pipe obstructions, gas formation, water hammer, and cleaning operations.Temperature changes may cause stress in the pipe Temperatures are changed byheated material as it enters cold pipe, by flushing, and by the use of hot fluids duringcleaning to remove grease Pipe should be designed to accommodate such stresses

3.2 Long-Distance Transport

Sludge/biosolids may be pumped for miles A pipeline is frequently less expensivethan the alternatives of trucks, rail cars, or barging (6), especially if, by pipelining,mechanical dewatering can be avoided Pipelines may have less environmental impactalong their routes than trucks

Tables 1.4 and 1.5 describe some typical pipelines for unstabilized and digestedsludge/biosolids An examination of these tables shows the following (1):

Cleveland, OH Easterly to Southerly

Indianapolis, IN Southport to Belmont

Jacksonville, FL District II to Buckman

Kansas City, MO West Side to Big Blue River

Philadelphia, PA Southeast to Southwest

waste-activated

Primary, waste-activated

accumulation at receiving plant

Thickeners do not work

as well on sludge that has been pumped from Southport

Heat treatment dewatering less

Good thickening at receiving plant

Good thickening at receiving plant

Source: US EPA (1).

Long pipeline carrying digested sludge/biosolids

Denver, CO

Rahway Valley Sanitary Authority, NJ

San Diego, CA Point Loma

Anaerobically digested primary

15 maximum

Source: US EPA (1).

1 Centrifugal pumps are widely used, even on unstabilized sludge/biosolids.

2 Operating pressures are usually below 125 pounds per square inch gauge (psig) (860 kN/m2 gauge).

3 Velocities are usually below 3.5 ft/s (1.1 m/s).

4 If the volatile solids content of the sludge/biosolids is low, the sludge/biosolids can be pumped at a high total solids concentration This is well illustrated by the lagoon sludge pipelines, which have operated at up to 18% solids; lagooned sludge has a very low volatile content.

In some cases, sludge/biosolids thickening at the receiving location was adverselyaffected by the shearing or the septicity that occurred in the pipelines Special flushingpractices after pipeline use, or use of a pipe cleaning device, was not done in severalcases The need for these techniques depends on the nature of the sludge/biosolids beingpumped

3.3 Headloss Calculations

sludge/biosolids have not been well defined because of their indefinite nature, andthat finite predictions of headlosses are impossible to make They are not available

in standard tables The approach has been to provide an adequate safety factor whendesigning sludge/biosolids pump and piping systems (7)

Head requirements for elevation change and velocity are the same as for water.However, friction losses may be much higher than friction losses in water pipelines Rel-atively simple procedures are often used in design work; such a procedure is describedbelow The accuracy of these procedures is often adequate, especially at solids contentsbelow 3% by weight However, as the pipe length, percent total solids, and percentvolatile solids increase, these simple procedures may give imprecise or misleadingresults In water piping, flow is almost always turbulent Formulas for friction losswith water, such as Hazen-Williams and Darcy-Weisbach, are based on turbulent flow.Sludge/biosolids also may flow turbulently, in which case the friction loss may beroughly that of water Sludge/biosolids, however, are unlike water in that laminar flowalso is common When laminar flow occurs, the friction loss may be much greater thanfor water Furthermore, laminar flow laws for ordinary newtonian fluids, such as water,cannot be used for laminar flow of sludge/biosolids because sludge/biosolids are not anewtonian fluid; it follows different flow laws

Figure 1.10 may be used to provide good estimates of friction loss under laminarflow conditions (1) Sludge/biosolids have been successfully and reliably pumped in thelaminar flow range Most of the installations operate in this range Figure 1.10 should beused in he following situations (1, 7):

1 Velocities are at least 2.5 ft/s (0.8 m/s) At lower velocities, the difference between sludge/biosolids and water may greatly increase.

2 Velocities do not exceed 8 ft/s (2.4 m/s) Higher velocities are not commonly used because

of high friction loss and abrasion problems.

3 Thixotropic behavior is not considered Thixotropy implies time-dependent change in viscosity that drops with time of shearing, followed by a gradual recovery when shearing