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## DISCLAIMER

This manual provides public water systems and drinking water primacy
agencies with guidance for complying with the turbidity provisions found
within the Interim Enhanced Surface Water Treatment Rule (IESWTR).

This document was issued in support of EPA regulations and policy
initiatives involving development and implementation of the IESWTR. This
document is EPA guidance only. It does not establish or affect legal
rights or obligation. EPA decisions in any particular case will be made
applying the laws and regulation on the basis of specific facts when
permits are issued or regulations promulgated.

Mention of trade names or commercial products does not constitute an EPA
endorsement or recommendation for use.

ACKNOWLEDGMENTS

The Environmental Protection Agency gratefully acknowledges the
assistance of the members of the Microbial and Disinfection Byproducts
Federal Advisory Committee and Technical Work Group for their comments
and suggestions to improve this document. EPA also wishes to thank the
representatives of drinking water utilities, researchers, and the
American Water Works Association for their review and comment. Finally
the Agency would like to recognize the individual contribution of the
following:

Randy Goss, City of Austin

Ray Letterman, Syracuse University

Mike Pickel, City of Philadelphia Water Department

Paul Gilbert Snyder, California Department of Health Services

Brian Tarbuck, Maine Department of Human Services

John Miller, Los Angeles Department of Water and Power

Blake Atkins, U.S. EPA Region VI

Eric Bissonette, U.S. EPA, OGWDW, TSC

Jon Bender, U.S. EPA, OGWDW, TSC

Ralph Flournoy, U.S. EPA Region VII

Jeff Robichaud, U.S. EPA, OGWDW

CONTENTS

1\. Introduction 1-1

1.1 Purpose of Document 1-1

1.2 Summary of Chapters 1-1

2\. Turbidity Requirements: IESWTR 2-1

2.1 Introduction 2-1

2.2 Regulatory Requirements 2-3

2.2.1 Applicability 2-3

2.2.2 Combined Filter Effluent Monitoring 2-3

2.2.3 Individual Filter Monitoring 2-8

2.3 Reporting and Recordkeeping 2-9

2.3.1 System Reporting Requirements 2-9

2.3.2 State Reporting Requirements 2-11

2.3.3 System Recordkeeping Requirements 2-12

2.3.4 State Recordkeeping Requirements 2-12

2.4 Additional Compliance Issues 2-12

2.4.1 Schedule 2-12

2.4.2 Individual Filter Follow-up Action 2-13

2.4.3 Notification 2-15

2.4.4 Variances and Exemptions 2-18

2.5 References 2-19

3\. Turbidity Methods & Measurement 3-1

3.1 Introduction 3-1

3.2 Approved Turbidity Methods 3-1

3.2.1 EPA Method 180.1 3-1

3.2.2 Standard Method 2130B 3-1

3.2.3 Great Lakes Instrument Method 2 (GLI 2) 3-2

3.3 Turbidimeters 3-2

3.3.1 Bench Top Turbidimeters 3-2

3.4 Quality Assurance/Quality Control 3-6

3.4.1 Quality Assurance Organization and Responsibilities 3-7

3.4.2 Quality Assurance Objectives 3-7

3.4.3 Standard Operating Procedures 3-7

3.4.4 Sampling Strategy and Procedures 3-9

3.4.5 Calibration 3-12

3.4.6 Data Screening, Validation, and Reporting 3-15

3.4.7 Performance and System Audits 3-16

3.4.8 Preventative Maintenance 3-16

3.5 Data Collection and Management 3-17

3.5.1 Data Collection Methods 3-17

3.5.2 Data Management 3-19

3.6 References 3-20

4\. Approach for Compliance 4-1

4.1 Compliance Approach for Turbidity Requirements 4-1

4.2 System Evaluation & Plant Optimization 4-1

4.2.1 Coagulation/Rapid Mixing 4-2

4.2.2 Flocculation 4-4

4.2.3 Sedimentation 4-6

4.2.4 Filtration 4-7

4.3 Process Enhancements/Technologies 4-8

4.4 References 4-9

5\. Individual Filter Self Assessment 5-1

5.1 Introduction 5-1

5.2 Developing A Filter Run Profile 5-4

5.3 Assessing Hydraulic Loading Conditions Of Filter 5-6

5.4 Assessing Condition & Placement Of Filter Media 5-7

5.5 Assessing Backwash Practices 5-8

5.6 Assessing Condition Of Support Media/Underdrains 5-12

5.7 Assessing Rate-Of-Flow Controllers & Filter Valve Infrastructure
5-14

5.8 References 5-14

6\. Comprehensive Performance Evaluation 6-1

6.1 Introduction 6-1

6.2 Background On The CPE 6-1

6.3 Components of a CPE 6-4

6.3.1 Performance Assessment 6-4

6.3.2 Major Unit Process Evaluation 6-7

6.3.3 Factors Limiting Performance 6-8

6.4 Activities During a CPE 6-10

6.5 CPE Quality Control 6-13

6.6 Next Steps 6-15

6.7 References 6-16

7\. Importance of Turbidity 7-1

7.1 Overview 7-1

7.2 Turbidity: Definition, Causes, and History as a Water Quality
Parameter 7-1

7.3 Turbidity\'s Significance to Human Health 7-4

7.3.1 Waterborne Disease Outbreaks 7-5

7.3.2 The Relationship Between Turbidity Removal and Pathogen Removal
7-7

7.4 References 7-10

8\. Particles Contributing to Turbidity 8-1

8.1 Introduction 8-1

8.2 Characteristic Properties of Particles 8-1

8.2.1 Particle Settling 8-2

8.2.2 Particle Density and Size Distribution 8-3

8.3 Inorganic Particles 8-4

8.3.1 Naturally Occurring Minerals 8-4

8.4 Organic Particles 8-5

8.4.1 Synthetic Organics 8-5

8.4.2 Natural Organic Matter (NOM) 8-5

8.4.3 Total Organic Carbon (TOC) 8-6

8.4.4 Organic Disinfection By-products (DBPs) 8-6

8.5 Particles of Biotic Origin 8-7

8.5.1 Protozoans 8-7

8.5.2 Viruses 8-8

8.5.3 Algae 8-9

8.5.4 Bacteria 8-9

8.6 Particles Added or Created During Treatment 8-13

8.6.1 Coagulants 8-13

8.6.2 Powdered Activated Carbon (PAC) 8-14

8.6.3 Recycle Flows 8-14

8.7 Electrokinetic Properties of Particles 8-14

8.7.1 Electrical Potential 8-15

8.7.2 Electrical Double Layer Theory 8-15

8.8 References 8-18

9\. Turbidity in Source Water 9-1

9.1 Introduction 9-1

9.2 Occurrence of Turbidity in Surface Water Supplies 9-1

9.2.1 Rivers 9-1

9.2.2 Lakes and Reservoirs 9-7

9.3 Ground Water Under the Direct Influence (GWUDI) 9-9

9.4 Additional Watershed Considerations 9-9

9.5 Water Sources Occurrence in the United States 9-10

9.6 References 9-11

10\. Turbidity Through the Treatment Processes 10-1

10.1 Introduction 10-1

10.2 Intake Facilities/Raw Water Screening 10-2

10.2.1 Intake Location 10-2

10.2.2 Intake Depth 10-2

10.2.3 Effect on Turbidity 10-3

10.3 Pre-sedimentation 10-3

10.3.1 Effect on Turbidity 10-3

10.4 Coagulation 10-4

10.4.1 Chemicals 10-4

10.4.2 Rapid Mixing 10-6

10.4.3 Effect on Turbidity 10-6

10.5 Flocculation 10-7

10.5.1 Slow Mixing 10-7

10.5.2 Detention Time 10-7

10.5.3 Effect on Turbidity 10-8

10.6 Sedimentation/Clarification 10-8

10.6.1 Effect on Turbidity 10-11

10.7 Filtration 10-11

10.7.1 Conventional Rapid Sand Filters 10-11

10.7.2 Slow Sand Filters 10-14

10.7.3 Pressure Filters 10-15

10.7.4 Precoat/Diatomaceous Earth Filters 10-16

10.7.5 Effect on Turbidity 10-16

10.8 Membrane Processes 10-17

10.8.1 Effect on Turbidity 10-20

10.9 Recycle Streams 10-20

10.9.1 Sources of Recycle Streams 10-21

10.9.2 Recycle Stream Quantity and Quality 10-21

10.9.3 Point of Recycle Stream Return 10-22

10.9.4 Effect on Turbidity 10-22

10.10 References 10-22

11\. Basic Turbidimeter Design and Concepts 11-1

11.1 Introduction 11-1

11.2 Turbidimeter Measuring Principles 11-1

11.2.1 Light Source 11-2

11.2.2 Sample Volume 11-3

11.2.3 Photodetector 11-3

11.3 Turbidimeter Design Configurations 11-3

11.3.1 Design Standards 11-4

11.3.2 Single Beam Design 11-5

11.3.3 Ratio Design 11-6

11.3.4 Modulated Four Beam Design 11-7

11.3.5 Surface Scatter Design 11-7

11.3.6 Transmittance Design 11-8

11.4 Types of Turbidimeters 11-8

11.4.1 Bench Top Turbidimeters 11-9

11.4.2 Portable Turbidimeters 11-9

11.4.3 On-Line Turbidimeters 11-10

11.5 References 11-11

#### APPENDIX A List of Definitions

#### APPENDIX B Determination of Turbidity by Nephelometry

#### APPENDIX C Turbidity Standard Method

APPENDIX D [Turbidity GLI Method 2]{.smallcaps}

FIGURES

Figure 2-1. Flowchart of IESWTR General Requirements 2-2

Figure 2-2. Flowchart of IESWTR Combined Filter Provisions for
Conventional and Direct Filtration Systems 2-5

Figure 2-3. Flowchart of IESWTR Combined Filter Provisions for
Alternative Filtration Technologies 2-6

Figure 2-4. Flowchart of SWTR Combined Filter Provisions for Slow Sand
and Diatomaceous Earth Filtration 2-7

Figure 2-5. Flowchart of IESWTR Individual Filter Provisions 2-10

Figure 2-6. Example Filter Profile 2-13

Figure 3-1. Calibration Checklist 3-16

Figure 5-1. Filter Run Profile -- Turbidity (NTU) vs. Time 5-5

Figure 5-2. Box Used for Excavation 5-7

Figure 5-3. Box Excavation Demonstration 5-8

Figure 5-4. Pipe Bed Expansion 5-11

Figure 5-5. Bed Expansion Device 5-11

Figure 5-6. On-Line Turbidimeters Showing Performance Problems Due to
Inoperable\
Rate-of-Flow Controllers 5-14

Figure 6-1. Capable Plant Model 6-2

Figure 6-2. An Example of Performance Assessment Using Historical Data
6-6

Figure 6-3. An Example of Individual Filter Data Collected During CPE
6-7

Figure 6-4. Example Performance Potential Graph 6-8

Figure 6-5. Activities During a CPE 6-12

Figure 7-1. Typical Sources of Turbidity in Drinking Water 7-2

Figure 7-2. Jackson Candle Turbidimeter 7-3

Figure 7-3. Nephelometric Turbidimeter 7-5

Figure 7-4. Particles of Turbidity May Provide Protection for
Microorganisms 7-6

Figure 7-5. Relationship Between Removal of *Giardia* and Turbidity 7-8

Figure 7-6. Relationship Between Removal of *Cryptosporidium* and
Turbidity 7-8

Figure 8-1. Particle Size Spectrum 8-2

Figure 8-2. Cryptosporidium Life Cycle 8-8

Figure 8-3. Plankton and Other Surface Water Algae 8-10

Figure 8-4. Filter Clogging Algae 8-11

Figure 8-5. Examples of Bacteria and Fungi Forms 8-12

Figure 8-6. Double Layer Theory (Guoy-Stern Colloidal Model) 8-16

Figure 9-1. The Natural Hydrologic Cycle 9-2

Figure 9-2. Typical Watershed 9-3

Figure 9-3. Sources of Contaminants in Raw Water Supplies 9-4

Figure 9-4. Turbidity Increase Event on the Missouri River at Omaha 9-6

Figure 9-5. Turbidity Increase Due to Forest Fire in Buffalo Creek 9-8

Figure 9-6. Raw Water Source by Water System Size 9-10

Figure 10-1. A Typical Conventional Water Treatment System 10-1

Figure 10-2. The Alum Coagulation Diagram and Its Relationship to Zeta
Potential 10-5

Figure 10-3. Circular Radial-flow Clarifier 10-9

Figure 10-4. Plate Settlers Used for High Rate Sedimentation 10-10

Figure 10-5. Accelerator Solids Contact Unit 10-10

Figure 10-6. Typical Rapid Sand Filter 10-12

Figure 10-7. Typical Covered Slow Sand Filter Installation 10-14

Figure 10-8. Cross Section of a Typical Pressure Filter 10-15

Figure 10-9. Typical Filter Run Showing Progress of Floc Penetration and
Effluent Turbidity 10-17

Figure 10-10. Pressure-Driven Membrane Process Application Guide 10-18

Figure 10-11. Typical Spiral-Wound Reverse Osmosis Membrane Module
Driven 10-19

Figure 10-12. Typical Hollow Fine-Fiber Reverse Osmosis Membrane Module
10-19

Figure 10-13. Representation of hollow-fiber UF module 10-20

Figure 11-1. Scattered Light at 90° 11-1

Figure 11-2. Angular Patterns of Scattered Light from Particles of
Different Sizes 11-2

Figure 11-3. Basic Nephelometer 11-5

Figure 11-4. Ratio Turbidimeter 11-6

Figure 11-5. Modulated Four-Beam Turbidimeter 11-7

Figure 11-6. Surface Scatter Turbidimeter 11-8

Figure 11-7. Bench Top Turbidimeter 11-9

Figure 11-8. Portable Turbidimeter 11-9

##### Tables

Table 5-1. Individual Filter Self Assessment Worksheet 5-3

Table 5-2. WTP Performance Deviation Trigger Events 5-5

Table 5-3. General Guide to Acceptable Filter Hydraulic Loading Rates
5-6

Table 5-4. Guidelines Regarding Acceptable Backwashing Practices 5-9

Table 5-5. Example Filter Support Gravel Placement Grid 5-13

Table 6-1. CCP Optimized Performance Goals 6-3

Table 6-2. Evaluation Team Capabilities 6-13

Table 6-3. Quality Control Checklist for Completed CPEs 6-14

Table 7-1. Cryptosporidium Outbreaks vs. Finished Water Turbidity 7-7

Table 7-2. Studies on the Relationship between Turbidity Removal and
Protozoa Removal 7-9

Table 10-1. Typical Feed Pressures for Pressure Driven Membrane
Processes 10-18

##### ACRONYMS

AIDs Acquired Immune Deficiency Syndrome

ASCE American Society of Civil Engineers

AWWA American Water Works Association

AWWARF American Water Works Association Research Foundation

CB Calibration Blank

CCP Composite Correction Program

CDC Centers for Disease Control

CDHS California Department of Health Services

CFR Code of Federal Regulations

CPE Comprehensive Performance Evaluation

CSO Combined Sewer Overflow

CTA Comprehensive Technical Assistance

CWSS Community Water System Survey

DCS Distributed Control Systems

DBP Disinfection Byproduct

DE Diatomaceous Earth

EPA Environmental Protection Agency

FR Federal Register

FTU Formazin Turbidity Units

GLI Great Lakes Instrument

GWUDI Ground Water Under the Direct Influence

HIV Human Immunodeficiency Virus

IESWTR Interim Enhanced Surface Water Treatment Rule

IPC Instrument Performance Check Solution

ISO International Organization for Standardization

JTU Jackson Turbidity Units

LAN Local Area Network

LCR Linear Calibration Range

LRB Laboratory Reagent Blank

LED Light Emitting Diode

MCL Maximum Contaminant Level

MSDS Material Safety Data Sheet

NAS National Academy of Sciences

NCEPI National Center for Environmental Publications and Information

NOM Natural Organic Matter

NPDES National Pollution Discharge Elimination System

NPDWR National Primary Drinking Water Regulation

NSF National Science Foundation

NTU Nephelometric Turbidity Units

PAC Powdered Activated Carbon

PC Personal Computer

PCAL Primary Calibration Standard

PCBs Polychlorinated Biphenyls

PWS Public Water System

QA Quality Assurance

QC Quality Control

QCS Quality Control Sample

RIA Regulatory Impact Analysis

SCADA Supervisory Control and Data Acquisition

SCAL Secondary Calibration Standards

SDWA Safe Drinking Water Act

SOP Standard Operating Procedure

SS Secondary Calibration Standard

SSS Stock Standard Suspension

SWTR Surface Water Treatment Rule

TOC Total Organic Carbon

THM Trihalomethane