SEPA Guidance Manual for Compliance with
i—" the Surface Water Treatment Rules:
Turbidity Provisions
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Office of Water (4606M)
EPA 815-R-20-004
June 2020
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Disclaimer
This document provides guidance to states, tribes, and U.S. Environmental Protection
Agency (EPA) exercising primary enforcement responsibility under the Safe Drinking
Water Act (SDWA) and contains EPA's policy recommendations for complying with the
suite of Surface Water Treatment Rules (SWTR). Throughout this document, the terms
"state" and "states" are used to refer to all types of primacy agencies including states,
U.S. territories, Indian tribes, and EPA.
The statutory provisions and EPA regulations described in this document contain legally
binding requirements. This document is not a regulation itself, nor does it change or
substitute for those provisions and regulations. Thus, it does not impose legally binding
requirements on EPA, states, or the regulated community. This guidance does not confer
legal rights or impose legal obligations upon any member of the public.
While EPA has made every effort to ensure the accuracy of the discussion in this
guidance, the obligations of the regulated community are determined by statutes,
regulations, or other legally binding requirements. In the event of a conflict between the
discussion in this document and any statute or regulation, this document would not be
controlling.
The general description provided here may not apply to a particular situation based
upon the circumstances. Interested parties are free to raise questions and objections
about the substance of this guidance and the appropriateness of the application of this
guidance to a particular situation. EPA and other decision makers retain the discretion to
adopt approaches on a case-by-case basis that differ from those described in this
guidance, where appropriate.
Mention of trade names or commercial products does not constitute endorsement or
recommendation for their use.
This is a living document and may be revised periodically without public notice. EPA
welcomes public input on this document at any time.
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Contents
CHAPTER 1 - Introduction 1
1.1 Purpose of Document 1
1.2 Overview of Suite of Surface Water Treatment Rules (SWTRs) 1
1.3 Other Applicable Rules 4
1.4 Summary of Chapters and Appendices 5
1.5 References 6
CHAPTER 2 - Turbidity Requirements 8
2.1 Introduction 8
2.2 Performance Standards and Monitoring Requirements 8
2.2.1 CFE Requirements 8
2.2.2 Special Provisions for PWSs that Use Lime Softening 16
2.2.3 IFE Turbidity Requirements 16
2.2.4 LT2ESWTR Toolbox Options 21
2.3 Reporting and Recordkeeping 24
2.3.1 CFE Reporting 24
2.3.2 IFE Reporting 24
2.3.3 LT2ESWTR Toolbox Reporting Requirements 25
2.3.4 Recordkeeping Requirements 26
2.4 Additional Compliance Issues 26
2.4.1 Individual Filter Follow-up Actions 27
2.4.2 Notification 28
2.5 References 30
CHAPTER 3 - Turbidity Methods & Measurement 33
3.1 Introduction 33
3.2 Approved Turbidity Methods 33
3.2.1 EPA Method 180.1 33
3.2.2 Standard Method 2130B 33
3.2.3 Great Lakes Instrument Method 2 (GLI 2) 33
3.2.4 Hach I iltei I rak Method 10133 34
3.3 Turbidimeters 34
3.3.1 Bench Top Turbidimeters 34
3.3.2 Continuous Turbidimeters 36
3.4 Quality Assurance/Quality Control (QA/QC) 38
3.4.1 QA Organization and Responsibilities 38
3.4.2 QA Objectives 38
3.4.3 SOPs 38
3.4.4 Sampling Strategy and Procedures 40
3.4.5 Calibration and Verification 43
3.4.6 Data Screening and Reporting 46
3.4.7 Performance and System Audits 46
3.4.8 Preventative Maintenance 46
3.5 Data Collection and Management 47
3.5.1 Data Collection Methods 47
3.5.2 Data Management 48
3.6 References 49
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CHAPTER 4 - Treatment Optimization 52
4.1 Introduction 52
4.2 Tools Available for Optimization 52
4.2.1 Composite Correction Program Approach 53
4.2.2 Area-Wide Optimization Program (AWOP) 53
4.3 Evaluating System Processes 56
4.3.1 Coagulation/Rapid Mixing 56
4.3.2 Flocculation 59
4.3.3 Sedimentation 61
4.3.4 Filtration 63
4.4 References 66
CHAPTER 5 - Individual Filter Self-Assessment 69
5.1 Introduction 69
5.2 Developing a Filter Profile 72
5.3 Assessing Hydraulic Loading Conditions of the Filter 76
5.4 Assessing Condition and Placement of Filter Media 79
5.4.1 Filter Inspection 79
5.4.2 Media Inspection 80
5.4.3 Media Placement and Observations 81
5.4.4 Media Analyses 81
5.4.5 Completing the Inspection 82
5.5 Assessing Condition of Support Media/Underdrains 82
5.6 Assessing Backwash Practices 84
5.6.1 Initiation of Backwash 84
5.6.2 Backwash Sequence 84
5.6.3 Identifying the Backwash Rate 85
5.6.4 Bed Expansion 86
5.6.5 Backwash Effectiveness 89
5.6.6 Backwash Rate 91
5.6.7 Terminating the Backwash 92
5.6.8 Backwash SOP 92
5.7 Assessment of Placing a Filter Back into Service 92
5.8 Assessing Rate-Of-Flow Controllers and Filter Valve Infrastructure 93
5.8.1 Leaking V alve s 94
5.8.2 Flow Meters 94
5.9 Other Considerations 94
5.10 Assessment of Applicability of Corrections 94
5.11 Preparation of the Report 95
5.12 References 95
CHAPTER 6 - Comprehensive Performance Evaluation (CPE) 97
6.1 Introduction 97
6.2 Background on the CPE 97
6.3 Components of a CPE 99
6.3.1 Performance Assessment 99
6.3.2 Major Unit Process Evaluation 103
6.3.3 Factors Limiting Performance 104
6.4 Activities During a CPE 107
6.5 CPE Quality Control (QC) Ill
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6.6 Next Steps 112
6.7 References 113
Appendices
Appendix A — Glossary A-l
Appendix B — Basic Turbidimeter Design and Concepts B-l
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Figures
Figure 2-1. Flowchart of CFE Turbidity Provisions for Conventional and Direct Filtration Systems 10
Figure 2-2. Flowchart of CFE Turbidity Provisions for Slow Sand and DE Filtration Systems 12
Figure 2-3. Slow Sand Filter in Idaho 13
Figure 2-4. Flowchart of CFE Turbidity Provisions for Alternative Filtration Systems 15
Figure 2-5. Cartridge Filters Installed at a Small PWS 16
Figure 2-6. Turbidity Monitoring Requirements for Conventional and Direct Filtration Plants [40 CFR
141.74(c)(1), 40 CFR 141.174, 40 CFR 141.560, and 141.562] 18
Figure 2-7. Example Filter Profile 27
Figure 3-1. Calibration Checklist 45
Figure 5-1. Example Filter Profile of Optimized Filter Performance 73
Figure 5-2. Example Filter Profile of Optimized Filter with Turbidity Spike During Filter Run 74
Figure 5-3. Example Filter Profile with Long and High Initial Spike 74
Figure 5-4. Example Filter Profile of Optimized Filter with Breakthrough at End of Filter Ru 75
Figure 5-5. Example Filter Profile with Multiple Spikes 75
Figure 5-6. Example Filter Profile with High Initial Spike and Turbidity Levels Above 1.0 NTU 76
Figure 5-7. Box Used for Excavation 80
Figure 5-8. Box Excavation Demonstration 80
Figure 5-9. Mudball from a Filter 81
Figure 5-10. Underdrain System 82
Figure 5-11. Examples of a Secchi Disk 88
Figure 5-12. "Pipe Organ" Expansion 89
Figure 5-13. Example of Floe Retention Analysis Results for 4-foot Deep Mono Media Filter Bed 91
Figure 5-14. Example of Floe Retention Analysis Results for 4-foot Deep Dual Media Filter Bed 91
Figure 6-1. An Example of Performance Assessment Using Historical Data 101
Figure 6-2. An Example of Individual Filter Data Collected During a CPE 103
Figure 6-3. Example Performance Potential Graph 104
Figure 6-4. Activities During a CPE 108
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Tables
Table 2-1. CFE and IFE Turbidity Monitoring Requirements for Conventional and Direct Filtration
Systems 17
Table 2-2. Follow-up Requirements in Response to IFE Turbidity Triggers (40 CFR 141.175(b) and 40
CFR 141.563) 19
Table 2-3. Microbial Toolbox Options that Incorporate Turbidity and their Turbidity Criteria [40 CFR
141.715(b)] 21
Table 2-4. Reporting Requirements for IFE Monitoring [40 CFR 141.175(b) and 141.570(b)] 25
Table 2-5. Turbidity Violations by Public Notification Tier [40 CFR 141 Subpart Q, Appendix A] 29
Table 5-1. Individual Filter Self-Assessment Worksheet 70
Table 5-2. Filter Performance Examples for Six Scenarios 72
Table 5-3. General Guide to Acceptable Filter Hydraulic Loading Rates1 76
Table 5-4. Example Filter Support Gravel Placement Grid Depth of Filter Support Gravels (in inches)
Measured from the Wash Water Trough 83
Table 5-5. Guidelines Regarding Acceptable Backwashing Practices 84
Table 6-1. CPE Treatment Performance Goals1 98
Table 6-2. Evaluation Team Capabilities 110
Table 6-3. QC Checklist for Completed CPEs Ill
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Acronyms
List of common abbreviations and acronyms used in this document and appendices:
AIDS
Acquired Immune Deficiency Syndrome
ASCE
American Society of Civil Engineers
AWOP
Area-wide Optimization Program
AWWA
American Water Works Association
AWWARF
American Water Works Association Research Foundation (now Water Research
Foundation)
CCP
Composite Correction Program
CDC
Centers for Disease Control
CFE
Combined Filter Effluent
CFR
Code of Federal Regulations
CPE
Comprehensive Performance Evaluation
CTA
Comprehensive Technical Assistance
CWS
Community Water System
CWSS
Community Water System Survey
DBP
Disinfection Byproduct
DBPR
Disinfectants and Disinfection Byproduct Rule
DCS
Distributed Control Systems
DE
Diatomaceous Earth
EPA
Environmental Protection Agency
FBRR
Filter Backwash Recycling Rule
FR
Federal Register
FTU
Formazin Turbidity Units
GLI 2
Great Lakes Instrument Method 2
GPM
Gallons per Minute
GWUDI
Ground Water Under the Direct Influence
HAA
Haloacetic Acids
HAA5
Haloacetic Acids (five)
IESWTR
Interim Enhanced Surface Water Treatment Rule
IFE
Individual Filter Effluent
IPC
Instrument Performance Check Solution
ISO
International Organization for Standardization
JTU
Jackson Turbidity Units
LRAA
Locational Running Annual Average
LRB
Laboratory Reagent Blank
LT IESWTR
Long Term 1 Enhanced Surface Water Treatment Rule
LT2ESWTR
Long Term 2 Enhanced Surface Water Treatment Rule
MCL
Maximum Contaminant Level
MGD
Million Gallons per Day
MPA
Microscopic Particulate Analysis
ML
Milliliter
MSDS
Material Safety Data Sheet
NAS
National Academy of Sciences
NOM
Natural Organic Matter
NPDES
National Pollution Discharge Elimination System
NPDWR
National Primary Drinking Water Regulation
NSF
National Science Foundation
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NTNCWS
Non-Transient Non-Community Water System
NTU
Nephelometric Turbidity Units
OSHA
Occupational Safety and Health Administration
PAC
Powdered Activated Carbon
PBT
Performance Based Training
PCAL
Primary Calibration Standard
PCBs
Polychlorinated Biphenyls
PN
Public Notification
PWS
Public Water System
QA
Quality Assurance
QC
Quality Control
RTCR
Revised Total Coliform Rule
SCADA
Supervisory Control and Data Acquisition
SCAL
Secondary Calibration Standard
SDWA
Safe Drinking Water Act
SOP
Standard Operating Procedure
SWTR
Surface Water Treatment Rule
TNCWS
Transient Non-Community Water System
TOC
Total Organic Carbon
TTHM
Total Trihalomethanes
XT
Treatment Technique
UV
Ultraviolet
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CHAPTER 1 - Introduction
1.1 Purpose of Document
The objective of the guidance manual is to provide public water
systems (PWSs) with guidance for complying with the turbidity
provisions found in the Surface Water Treatment Rule (SWTR),
Interim Enhanced Surface Water Treatment Rule (IESWTR), Long
Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR),
and Long Term 2 Enhanced Surface Water Treatment Rule
(LT2ESWTR). The primary audience for the guidance manual is
utility personnel at PWSs that utilize filtration and the staff of state
drinking water programs that work with PWSs to protect water
quality.
The original guidance manual (USEPA, 1999) focused on the requirements of the IESWTR as it relates to
turbidity. This guidance manual focuses on technical information regarding specific requirements of the
IESWTR, LT1ESWTR, and LT2ESWTR relating to turbidity. It is intended for experienced operators and
others in the regulated community.
Copies of this document and other referenced documents can be obtained by:
• Contacting the appropriate state office.
• Accessing U.S. Environmental Protection Agency's (EPA) Safe Drinking Water website at
https://www.epa.gov/ground-water-and-drinking-water/safe-drinking-water-hotline.
• Downloading from EPA's website at: https://www.epa.gov/dwreginfo/guidance-manuals-surface-
water-treatment-rules.
• Calling the National Service Center for Environmental Publications at 1-800-490-9198 or visiting
its website at: www.epa.gov/ncepihom/.
1.2 Overview of Suite of Surface Water Treatment Rules
(SWTRs)
SWTR
Under the 1989 SWTR (USEPA, 1989), EPA established treatment requirements for all PWSs using
surface water or ground water under the direct influence (GWUDI) of surface water as a source. The
requirements listed in 40 Code of Federal Regulations (CFR) 141.70 through 141.75 are intended to
protect against the adverse health effects associated with Giardia lamblia, viruses, and Legionella and
include:
• Maintenance of a disinfectant residual in water entering, and within the distribution system.
In this
chapter:
•
Purpose of Document
•
Ch'er\'iew of SWTR,
IESWTR, LT1ESWTR,
and LT2ESWTR
•
Other Applicable Rules
•
Summary of chapters
and appendices
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• Removal/inactivation of at least 99.9 percent (3-log) of Giardia and 99.99 percent (4-log) of
viruses.
• Filtration, unless PWSs meet specified avoidance criteria.
• For filtered PWSs, a turbidity limit for the combined filter effluent (CFE) of 5 nephelometric
turbidity units (NTUs) at any time, and a limit of 0.5 NTU in 95 percent of measurements each
month for treatment plants using conventional treatment or direct filtration (with separate
standards for other filtration technologies). These requirements were superseded by the 1998
IESWTR and the 2002 LT1ESWTR.
• Watershed control programs and water quality requirements for unfiltered PWSs.
PWSs that qualify for filtration avoidance determinations must meet source water quality and site-specific
conditions to remain unfiltered. If any of the criteria for avoiding filtration are not met, PWSs must install
filtration treatment within 18 months of the failure. One of the avoidance criteria established by the
SWTR and later enhanced by the IESWTR and LTIESWTR is that turbidity levels cannot exceed 5 NTU
in the water immediately prior to the first point of disinfectant application. Turbidity measurements must
be made at least once every four hours, and a filtration avoidance PWS must report to its primacy agency
within 24 hours if it has exceeded the 5 NTU standard (40 CFR 141.71). This guidance manual does not
further address the turbidity requirements for filtration avoidance PWSs. Unfiltered PWSs should discuss
with their primacy agencies the requirements for successfully maintaining filtration avoidance status.
IESWTR
The IESWTR (USEPA, 1998) applies to PWSs serving at least 10,000 people and using surface water or
GWUDI as a source. These PWSs were to comply with the IESWTR by January 2002. The requirements
listed in 40 CFR 141.170 through 141.175 include:
• Removal of 99 percent (2-log) of Cryptosporidium for PWSs that provide filtration.
• For treatment plants using conventional treatment or direct filtration, a turbidity performance
standard for the CFE of 1 NTU as a maximum, and 0.3 NTU as a maximum in 95 percent of
monthly measurements, based on 4-hour monitoring (these limits supersede the SWTR turbidity
limits).
• Continuous monitoring of individual filter effluent (IFE) turbidity in conventional and direct
filtration plants and recording of IFE turbidity readings every 15 minutes.
• Filter profiles and/or assessments required under different monitoring results and scenarios, as
detailed in Section 2.2.3 of this report.
• PWSs using alternative filtration techniques [defined as filtration other than conventional, direct,
slow sand, or diatomaceous earth (DE)] must demonstrate to the state the ability to consistently
achieve 2-log removal of Cryptosporidium and comply with specific state-established CFE
turbidity requirements.
• The development of a disinfection profile and benchmark (to assess the level of microbial
protection provided), before facilities change their disinfection practices in order to also meet the
requirements of the Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR).
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• Cryptosporidium in the definition of GWUDI and in the watershed control requirements for
unfiltered PWSs.
• All new finished water reservoirs must be covered [40 CFR 141.170(c)].
LT1ESWTR
The LT1ESWTR (USEPA, 2002) extends most of the requirements of the IESWTR to surface water and
GWUDI PWSs serving fewer than 10,000 people.
The LT1ESWTR requirements listed in 40 CFR 141.500 through 141.571 differ from the IESWTR in a
few ways, including:
• If the PWS has two or fewer filters, it can perform continuous monitoring of the CFE in lieu of
IFE monitoring.
• If turbidity monitoring equipment fails, a PWS has 14 days (rather than 5 working days under
IESWTR) to resume continuous monitoring before incurring a violation.
• If the IFE turbidity exceeds 1.0 NTU for two or more consecutive 15-minute readings in one
month, the PWS must report the cause of the turbidity exceedance, if known, but a filter profile is
not required.
• If the IFE turbidity exceeds 2.0 NTU in two or more consecutive 15-minute readings for two
months in a row, the PWS must arrange a Comprehensive Performance Evaluation (CPE) no later
than 60 days after the filter exceeded 2.0 NTU for the second straight month (30 days under the
IESWTR), and it must be completed, and the report submitted to the state within 120 days after
the final exceedance (90 days under the IESWTR).
• Disinfection profiling requirements do not apply to transient noncommunity water systems
(TNCWSs).
• PWSs are required to monitor weekly (rather than daily) when preparing a disinfection profile.
• PWSs using either chloramines, ozone, or chlorine dioxide for primary disinfection are required
to complete a disinfection profile (PWSs using chlorine dioxide for primary disinfection under
IESWTR were not required to complete a profile).
LT2ESWTR
EPA promulgated the LT2ESWTR in 2006 (USEPA, 2006a). The LT2ESWTR builds upon the
requirements established by the SWTR, IESWTR, and the LT1ESWTR and can be found in 40 CFR
141.700 through 141.722. Key provisions of the LT2ESWTR include:
• Source water monitoring for Cryptosporidium, with reduced monitoring requirements for small
PWSs.
• Additional Cryptosporidium treatment technique (TT) provisions for certain filtered PWSs based
on source water Cryptosporidium concentrations.
• A variety of source, pre-filtration, treatment, additional filtration, and inactivation toolbox
components for PWSs to use to receive Cryptosporidium credit.
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• A requirement for inactivation of Cryptosporidium for all unfiltered PWSs.
• Requirements that PWSs conduct disinfection profiling and benchmarking to ensure continued
levels of microbial protection while PWSs take the necessary steps to comply with new
disinfection byproduct (DBP) standards.
• Requiring PWSs to cover an uncovered finished water reservoir or treat the water exiting the
uncovered finished water reservoir prior to entering into the distribution system.
1.3 Other Applicable Rules
Other drinking water regulations may affect how successfully a PWS complies with the turbidity
requirements of the SWTRs. Brief summaries of those regulations are provided in this section.
Filter Backwash Recycling Rule (FBRR)
The FBRR was published by EPA on June 8, 2001 (USEPA, 2001), and affects PWSs that meet all of the
following criteria:
• The PWS is a surface water system or GWUDI system.
• The PWS treats water using conventional or direct filtration.
• The PWS recycles one or more of the following: spent filter backwash, thickener supernatant, or
liquids from dewatering devices.
Affected PWSs were required to report information about their system to the state by December 8, 2003.
The FBRR also requires regulated recycle streams to be returned through all processes of a PWS's
existing conventional or direct filtration system or at an alternate location approved by the state. In
addition, the FBRR has recordkeeping requirements for affected PWSs.
Revised Total Coliform Rule (RTCR)
The RTCR (USEPA, 2013) sets maximum contaminant levels (MCLs) and maximum contaminant level
goals (MCLGs) for E. coli, sets a total coliform treatment technique (TT) requirement, and requires every
regulated PWS to periodically collect samples and analyze them for total coliforms. The number of
routine samples required each month depends on the system size. Samples must be collected according to
a written Sample Siting Plan [40 CFR 141.853(a)]. Assessments and corrective action are required when
monitoring results show that PWSs may be vulnerable to contamination.
Stage 2 Disinfectants and Disinfection Byproduct Rule (DBPR)
The requirements of the Stage 2 DBPR (USEPA, 2006b) apply to all community water systems (CWSs)
and non-transient non-community water systems (NTNCWSs) that uses a primary or residual disinfectant
other than ultraviolet (UV) light, or that deliver water that has been treated with a primary or residual
disinfectant other than UV light.
The numerical MCLs for the Stage 2 DBPR are 0.080 mg/L for total trihalomethanes (TTHMs), and
0.060 mg/L for the five regulated haloacetic acids (HAA5). Compliance determinations for the Stage 2
DBPR are based on a locational running annual average (LRAA) (i.e., compliance must be met at each
monitoring location) [40 CFR 141.620(a)]. EPA has adopted a population-based monitoring approach for
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the Stage 2 DBPR, where compliance monitoring requirements are based only on source water type and
retail population served.
Because Stage 2 DBPR MCL compliance for some PWSs is based on individual DBP measurements at a
location averaged over a four-quarter period, a PWS could measure higher TTHM or HAA5 levels than
the MCL values, while at the same time maintaining compliance with the rule. This is because the high
concentration could be averaged with lower concentrations at a given location. For this reason, the Stage
2 DBPR includes a requirement for operational evaluations that investigate the cause(s) of the high
TTHM or HAA5 concentrations. A PWS has exceeded an operational evaluation level at any monitoring
location when the sum of the two previous quarters' compliance monitoring results plus twice the current
quarter's result, divided by four, exceeds 0.080 mg/L for TTHM or 0.060 mg/L for HAA5. If an
operational evaluation level is exceeded, the PWS must conduct an "operational evaluation" and submit a
written report of the evaluation to the state (40 CFR 141.626).
1.4 Summary of Chapters and Appendices
As noted, the document is divided into two parts. The main body of the manual (Chapters 1 through 6)
outlines the specific turbidity requirements of the suite of SWTRs and includes information directly
applicable to complying with those requirements. The remainder of the main body of this document
consists of:
Chapter 2 - Turbidity Requirements
Chapter 2 outlines the regulatory requirements, reporting and recordkeeping requirements, and
additional compliance aspects of the suite of SWTRs related to turbidity.
Chapter 3 - Turbidity Methods & Measurement
Chapter 3 provides information regarding approved turbidity methods, analytical issues
associated with turbidimeters and turbidity measurement, quality assurance and quality control
issues (QA/QC), and data collection and management issues.
Chapter 4 - Treatment Optimization
Chapter 4 provides information on compliance with turbidity requirements. This chapter focuses
on plant optimization; highlighting areas which PWSs can most often improve to optimize water
treatment.
Chapter 5 - Individual Filter Self-Assessment
Chapter 5 provides detailed guidance on conducting a filter self-assessment including a
discussion of necessary components such as conducting filter profiles, assessing hydraulic
loading conditions, and assessing support media and underdrains.
Chapter 6 - Comprehensive Performance Evaluation
Chapter 6 provides a general overview of the Composite Correction Program (CCP) and
specifically the first component of the CCP, the CPE. Fundamental concepts are discussed
including major CPE components, standard CPE activities and CPE QC measures. PWSs may be
required to arrange for a CPE based on individual filter monitoring results.
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The appendices to the manual provide additional information for readers related to the terminology and
measuring of turbidity, including:
Appendix A - Glossary
Appendix A provides a list of definitions for terms used in the Guidance as well as other useful
terms associated with turbidity.
Appendix B - Basic Turbidimeter Design and Concepts
Appendix B provides basic information on turbidimeter designs, measuring principles, design
configurations, and various types of turbidimeters.
1.5 References
USEPA. 1989. National Primary Drinking Water Regulations: Surface Water Treatment Rule; Final Rule.
54 FR 27486. June 29, 1989. Available at:
http://water.epa.gov/lawsregs/rulesregs/sdwa/swtr/upload/SWTR.pdf.
USEPA. 1998. National Primary Drinking Water Regulations: Interim Enhanced Surface Water
Treatment Rule; Final Rule. 63 FR 69478. December 16, 1998. Available at:
http://www.gpo.gov/fdsvs/pkg/FR-1998-12-16/pdf/98-32888.pdf.
USEPA. 1999. Guidance Manual for Compliance with the Interim Enhanced Surface Water Treatment
Rule: Turbidity Provisions. EPA 815-R-99-010.
USEPA. 2001. National Primary Drinking Water; Filter Backwash Recycling Rule; Final Rule. 66 FR
31086. June 8, 2001. Available at: https://www.gpo.gov/fdsvs/pkg/FR-2001-06-08/pdf/01-13776.pdf.
USEPA. 2002. National Primary Drinking Water Regulations: Long Term 1 Enhanced Surface Water
Treatment Rule; Final Rule. 67 FR 1811. January 14, 2002. Available at:
https://www.gpo.gov/fdsvs/pkg/FR-2002-01-14/pdf/02-409.pdf.
USEPA. 2006a. National Primary Drinking Water Regulations: Long Term 2 Enhanced Surface Water
Treatment Rule; Final Rule. 71 FR 653. January 5, 2006. Available at: http://www.gpo.gov/fdsvs/pkg/FR-
2006-01-05/pdff 06-4.pdf.
USEPA. 2006b. National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection
Byproducts Rule; Final Rule. 71 FR 388, January 4, 2006 Available at:
https://www.gpo.gov/fdsvs/pkg/FR-2006-01-04/pdf/06-3.pdf.
USEPA. 2013. National Primary Drinking Water Regulations: Revisions to the Total Coliform Rule;
Final Rule. 78 FR 10269, minor corrections 79 FR 10665, February 13, 2013. Available at:
https://www.gpo.gov/fdsvs/pkg/FR-2013-02-13/pdf/2012-31205.pdf.
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CHAPTER 2 - Turbidity
Requirements
2.1 Introduction
This chapter outlines the regulatory requirements for turbidity
including established turbidity performance standards by treatment
technology, monitoring requirements, reporting requirements,
recordkeeping requirements, and additional compliance aspects of
the suite of SWTRs related to turbidity.
These requirements apply to PWSs that use surface water or
GWUDI of surface water and treat their water with filtration. Any
variations to the requirements based on system size will be noted where applicable. Turbidity
requirements for PWSs that meet criteria to avoid filtration are discussed briefly in Section 1.2, but not
covered in detail in this manual.
2.2 Performance Standards and Monitoring Requirements
As described in Chapter 1, the suite of SWTRs contains several key requirements related to turbidity. This
Section will discuss requirements for CFE turbidity performance standards by treatment technology, IFE
turbidity monitoring requirements, other requirements related to turbidity, and LT2ESWTR Toolbox
options where turbidity is used to measure performance.
2.2.1 CFE Requirements
CFE is generated when the effluent water from individual filters in operation is combined into one stream.
PWSs that use surface water or GWUDI of surface water and apply filtration treatment must monitor
turbidity in the CFE using an approved method (discussed in Section 3.2) (40 CFR 141.173 and 40 CFR
141.550). PWSs that only have a single filter do not have a "combined" filter effluent. However, for the
purposes of this document, all filter effluent will be referred to as CFE.
The CFE turbidity standards and some aspects of CFE turbidity monitoring vary by treatment technology.
The following Sections discuss the standards and monitoring requirements based on three groups of
treatment technologies:
• Conventional and Direct Filtration
• Slow Sand and DE Filtration
• Other Treatment Technologies (Alternative Filtration)
2.2.1.1 Conventional and Direct Filtration
Conventional filtration is defined as a series of processes including coagulation, flocculation,
sedimentation, and filtration resulting in substantial particulate removal. Direct filtration is defined as a
series of processes including coagulation and filtration (but excluding sedimentation), also resulting in
substantial particle removal.
In this chapter:
• Turbidity Performance
Standards and
Monitoring
Requirements
• Reporting and
Recordkeeping
• Additional Compliance
Issues
• References
Guidance Manual for Compliance with the 8
Surface Water Treatment Rules: Turbidity Provisions
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Turbidity Standards
For conventional and direct filtration systems, the turbidity standard of
representative samples of a PWS's filtered water must be less than or
equal to 0.3 NTU in at least 95 percent of the measurements taken each
month. The turbidity standard of representative samples of a PWS's
filtered water must not exceed 1 NTU at any time. As discussed in
Section 1.2, these turbidity standards were introduced with the
promulgation of the IESWTR and LT1ESWTR and are more stringent
than the original turbidity standards required by the SWTR (40 CFR
141.173 and 40 CFR 141.551).
Monitoring Requirements
CFE turbidity must be measured every four hours during plant operation [40 CFR 141.74(c)(1)].
Monitoring frequency may be reduced for PWSs serving 500 or fewer persons to once per day if the state
determines that less frequent monitoring is sufficient to indicate effective filtration performance.
Likewise, the state may require additional or more frequent monitoring for conventional or direct
filtration systems of any size. PWSs should check with their state about their CFE turbidity monitoring
requirements to ensure they are meeting state requirements.
A PWS may substitute CFE continuous turbidity monitoring for grab sample monitoring if the continuous
turbidimeters are validated for accuracy on a regular basis using a protocol approved by the state.
Figure 2-1 presents a flowchart of the CFE turbidity provisions for conventional and direct filtration
systems.
Conventional and direct
filtration CFE turbidity
standards are:
> Less than or equal to 0.3
NTU in 95 percent of
measurements
> 1 NTU maximum
Guidance Manual for Compliance with the 9
Surface Water Treatment Rules: Turbidity Provisions
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the PUS p«K>oe
n. ^tracer'
"V
r
fm
X
Does tne ^ A 3 *r-p-ay
c5rwent,onat c direct
"•*¦, * fraticn7
Ccr fe'cwamerfrts aTe rcot app. rcab e
to metered PWSs Far unf-'ter-sd
P'uVSs, tyb(ditv is measured
.nrnedtate y cwior to the first poi.it of
disinfectant application
See 5e"tor« i 2 for more fn^ormaricn
..•• "hoer the PWS «rrplcf slow""
'""'--v._ sand or diatomgceoui ...
fca-rtl futraticn^ .
P,VSi must OTipiv »vftft
CPS requirements *s-
a'tenat-ve Gratia n
figure 2-4^
v
'tes
,f
' PifrSs rrtusx omptv '.vtft CFE -
requirement: *cr slow sand'
th3tor"3rC*i>us earth ^
filtrstiOR ,Ftgu'e 2-2;
Aif PVvSs using corw»n:iG.rwrt c srrert ;
fi'tTatM3Ti must compfy with the 5 %v "*¦*.. ,
iE5'.». TF and CFE (*-
reauj'enents pert»m.ig to j
con\sntiDna'1-asr«c': '^ratoi systems
Did thfi FWS mor. tor
combined fi'te* efkyrt rjrb
-.. at 4-hDur nte-vaii'*
"vVs.s tuTSid^ ^ to 0.3 MTU in a.'
.^east 95:t of the measurements ..
""" ^-tsKei for tne no nth*.
fes
JL
Dmj turs-dit, exceea 1 IW
at anv time"'
"\'OlaMn
D-ritKePWS report CFE "
._ji55s jfe^ients to The state ov the.
""" i-D11 cfths month"51
'V
ves
-HO—kj Mi
P Vlegation1
1. In accordance with the SWTR [40 CFR 141.74 (c)(1)], the state may reduce this monitoring frequency for PWSs serving 500
or fewer persons to one sample per day if the state determines that less frequent monitoring is sufficient to indicate effective
filtration performance.
2. PWSs must consult with their state no later than 24 hours after learning of the violation in accordance with the Public
Notification Rule [40 CFR 141.203(b)(3)],
3. This violation requires public notification. The required Tier of public notification can be found in Appendix A to Subpart Q
of 40 CFR Section 141.
4. PWSs must report to the state the total number of CFE turbidity measurements taken during the previous month, the
number and percentage of CFE turbidity measurements that were less than or equal to 0.3 NTU, and the date and value of
any CFE turbidity measurements exceeding 1 NTU [40 CFR 141.175(a) and 141.570(a)],
Figure 2-1. Flowchart of CFE Turbidity Provisions for Conventional and Direct Filtration
Systems
Guidance Manual for Compliance with the 10
Surface Water Treatment Rules: Turbidity Provisions
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2.2.1.2 Slow Sand & Diatomaceous Earth (DE) Filtration
Unlike the other filtration technologies, the turbidity standards for slow sand and DE filters did not
change from the original SWTR. These technologies accomplish 2-log Cryptosporidium removal with the
turbidity limits set in the SWTR.
Turbidity Standards
For slow sand and DE filtration systems, the turbidity standard of
representative samples of a PWS's filtered water must be less than or
equal to 1 NTU in at least 95 percent of the measurements taken each
month. The state may allow a higher turbidity limit if the state
determines there is no significant interference with disinfection at the
higher level. However, at no time can the turbidity standard exceed 5
NTU [40 CFR 141.73(b) and (c)].
Monitoring Requirements
CFE turbidity must be measured every four hours that the PWS serves water to the public [40 CFR
141.74(c)(1)]. For slow sand filtration systems of any size and DE systems serving 500 or fewer persons,
the state may reduce the sampling frequency to once per day if the state determines that less frequent
monitoring is sufficient to indicate effective filtration performance. Likewise, the state may require
additional or more frequent monitoring for slow sand or DE systems of any size. PWSs should check with
their states about their system's CFE turbidity monitoring requirements to ensure they are meeting state
requirements.
A PWS may substitute continuous CFE turbidity monitoring for grab sample monitoring if the continuous
turbidimeter is validated for accuracy on a regular basis using a protocol approved by the state.
Figure 2-2 presents a flowchart of combined filter provisions for slow sand and DE filtration. Figure 2-3
shows a slow sand filter in Idaho.
Slow sand and DE CFE
turbidity standards are
> Less than or equal to 1
NTU in 95 percent of
measurements unless
state allows a higher
limit
> 5 NTU maximum
Guidance Manual for Compliance with the 11
Surface Water Treatment Rules: Turbidity Provisions
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Doe: the PWS pre* de
fHtratra*^ . '
T
Does tne PW5 employ
,soa' sar^ ijr oratcrraceo.fs^
earth "Hirst on"1
i CFE requirements are rot app^csrfcie I
[ tc unfilte^ed PW'Ls. For imP'tered
PVtfis Surbidrtvb measured i
1 ° *1 immediately p«"-Dr tc the- f rst ps'nt of >
[ cris nfectarrc app> ication
I See section 1.2 for mors inforrrat o |