United States
Environmental
Protection Agency
Office of Water
(4601)
EPA815-C-01-001
April 2001
LOW-PRESSURE MEMBRANE FILTRATION
FOR PATHOGEN REMOVAL: APPLICATION,
IMPLEMENTATION, AND REGULATORY
ISSUES

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LOW-PRESSURE MEMBRANE FILTRATION FOR PATHOGEN REMOVAL:
    APPLICATION, IMPLEMENTATION, AND REGULATORY ISSUES
                              Prepared for:
          UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
            OFFICE OF GROUND WATER AND DRINKING WATER
              STANDARDS AND RISK MANAGEMENT DIVISION
                      TECHNICAL SUPPORT CENTER
                       26 W. Martin Luther King Drive
                          Cincinnati, Ohio 45268
                              Prepared by:
                        MALCOLM PIRNIE, INC.
                     11832 Rock Landing Drive, Suite 400
                       Newport News, Virginia 23606

                              CH2M HILL
                             P.O. Box 28440
                          Tempe, Arizona 85285

                     SEPARATION PROCESSES, INC.
                     960 San Marcos Boulevard, Suite 200
                        San Marcos, California 92069
    Under Cadmus Group, Inc. Contract 68-C-00-113, Work Assignments 0-03 and 1-03

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ACKNOWLEDGEMENTS
This document was prepared by the United States Environmental Protection Agency, Office of
Ground Water  and  Drinking Water,  Standards and  Risk Management  Division, Technical
Support Center.  The Task Order Project Officer was Steven Allgeier. The Contract Project
Officer was Brenda Graves.

Technical consultants played a significant role in the research performed and preparation of this
document.   This work  was conducted  jointly  by Malcolm Pirnie,  Inc.,  CH2M Hill, and
Separation Processes, Inc. under The Cadmus Group Contract 68-C-00-113, Work Assignments
0-03 and 1-03.  Curtis Haymore of Cadmus was the  Project Manager.  The Malcolm Pirnie
project team was led by Chris Hill and included Brent Alspach, Anne Jack, and Christine Cotton.
Jim Lozier of CH2M Hill and Jim Vickers of Separation Processes provided technical direction
and guidance. Special thanks to the following, who provided technical review of the report.

Gil F. Crozes, Carollo Engineers
Joe G. Jacangelo, Montgomery Watson
Larry B. Landsness, Wisconsin Department of Natural Resources
Christopher R. McMeen,  Washington State Department of Health
Richard Puckett,  Virginia Department of Health
Richard H. Sakaji, California Department of Health Services
Jack C. Schulze, Texas Natural Resources Conservation Commission
Bruce A. Utne, Newport News (Virginia) Waterworks

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

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                              TABLE OF CONTENTS
EXECUTIVE SUMMARY.	ix
1.0 INTRODUCTION	1

   l.l  PURPOSE	2
   1.2  METHODOLOGY	2
    7.2.7  NSFInternational	2
    1.2.2  MF/UF Equipment Suppliers	4
    1.2.3   Utilities	4
    1.2.4  State Regulatory Agencies	4
   1.3  REPORT OVERVIEW	4

2.0 BACKGROUND	7
  2.1  REGULATORY HISTORY	7
    2.7.7  Surface Water Treatment Rule	8
    2.1.2  Interim Enhanced Surface Water Treatment Rule	9
    2.1.3  Long Term 1 Enhanced Surface Water Treatment Rule	10
    2.1.4  Filter Backwash Rule	10
    2.1.5  Long Term 2 Enhanced Surface Water Treatment Rule	10
    2.1.6  Stage 1 Disinfectants and Disinfection Byproducts Rule	73
    2.7.7  Stage 2 Disinfectants and Disinfection Byproducts Rule.	14
  2.2  MEMBRANE FILTRATION	15
    2.2.7  Overview of Low-Pressure Membrane Filtration	75
    2.2.2   The Use ofMicrofiltration and Ultrafiltration in the United States	27
      2.2.2.1 Treatment Capacity	21
      2.2.2.2 Source Water	23
      2.2.2.3 Manufacturer	23
      2.2.2.4 Geographic Location	24
      2.2.2.5 Installation Trends and Treatment Capacity	27
3.0 MICROBIAL REMOVAL	29

  3.1  INTRODUCTION	29
  3.2  PROTOZOAN CYSTS	30
  3.3  BACTERIA	37
  3.4  VIRUSES	42
  3.5  ALGAE	46
  3.6  SURROGATE CHALLENGE PARAMETERS	46
  3.7  SUMMARY	50

4.0 INTEGRITY TESTING	51
  4.1  OVER VIEW OF INTEGRITY TESTING	51

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  4.2 DIRECT METHODS	53
    4.2.1  Pressure Hold Test	54
    4.2.2  Diffusive Air Flow Test	56
    4.2.3  Sonic Sensing Analysis	57
    4.2.4  Bubble Point Testing	55
  4.3 INDIRECT METHODS	59
    4.3.1  Particle Counting	60
    4.3.2  Particle Monitoring	62
    4.3.3  Turbidity Measurements	63
    4.3.4  Other Indirect Methods	64
5.0  MEMBRANE INTEGRITY AND MICROBIAL RISK	65

  5.1 DRIVING FORCE FOR INTEGRITY TESTING	65
  5.2 INTEGRITY BREACHES	66
  5.3 FACTORS AFFECTING DIRECT METHODS	66
    5.3.7  Pressure-Driven Methods	66
    5.3.2  Sonic Methods	69
  5.4 FACTORS AFFECTING INDIRECT METHODS	69
    5.4.1  Common Factors Affecting Indirect Method Sensitivity	69
    5.4.2  Particle Counters	72
    5.4.3  Turbidimeters	72
  5.5 REGULATORY IMPLICATIONS OF INTEGRITY TESTING	73
    5.5.7  Framework for Minimizing Microbial Risk	73
    5.5.2  Implications of Current Integrity Test Methods	74
    5.5.3  Implications of Potential Future Integrity Test Methods	74
6.0  REGULATORY APPROACHES TO MICROFILTRATION AND
    ULTRAFILTRATION	77
  6.1 INTRODUCTION	77
  6.2 SUMMARY OF STATE REGULATORY APPROACHES	78
  6.3 INITIAL PRODUCT EVALUATION	84
  6.4 PILOT TESTING REQUIREMENTS	86
  6.5 DETERMINATION OF REMOVAL CREDITS	87
  6.6 INTEGRITY TESTING REQUIREMENTS	89
  6.7 SUMMARY	92

7.0  UTILITY PRACTICES	95
  7.1 INTRODUCTION	95
  7.2 DECISION DRIVERS	95
  7.3 OPERATIONAL PRACTICES	100
     7.3.7  Pretreatment	100
     7.3.2  Flux and Transmembrane Pressure	104
     7.3.3  Backwash Practices	104
     7.3.4  Clean-in-Place Practices	106
     7.3.5  Monitoring and Integrity Testing	707
     7.3.6  Treatment Challenges	705
  7.4 SUMMARY	108

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8.0  SUMMARY AND CONCLUSIONS	Ill

9.0  REFERENCES	117


APPENDIX A: LIST OF FULL-SCALE MF/UF FACILITIES IN THE UNITED STATES
             (AS OF JUNE 2000)	127
                                in

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                                 LIST OF TABLES
1  Project Data Elements	3
2  LT2ESWTR Bin Requirements	11
3  LT2ESWTR Microbial Toolbox Components	12
4  Required TOC Removal by Enhanced Coagulation and Enhanced Softening	13
5  Effect of Water Temperature on Flux	20
6  ICR Monitoring - Giardia and Cryptosporidium Occurrence Summary	30
7  MF andUF Studies Documenting Giardia Removal Efficiency	32
8  MF andUF Studies Documenting Cryptosporidium Removal Efficiency	35
9  MF andUF Studies Documenting Bacteria Removal Efficiency	38
10 MF and UF Studies Documenting Virus Removal Efficiency.	44
11 MF and UF Studies Documenting Algae Removal Efficiency	48
12 MF and UF Studies Documenting Particle Count Removal Efficiency.	49
13 Summary of Integrity Monitoring Methods	52
14 Summary of State Primacy Agency Regulatory Requirements	79
15 Summary of General Information for the Utilities Contacted	96
16 Summary of Operating Practices for Utilities Contacted	101

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                                 LIST OF FIGURES
1  Membrane Process Classification	16
2  Photomicrograph of a Hollow Fiber	16
3  Schematic of Asymmetric and Composite Membranes	17
4  Typical Hollow Fiber Module Configuration	17
5  Schematic of Membrane Flow Configurations	18
6  Distribution of Installed Membrane Treatment Capacity as of April 2000	22
7  Distribution of Membrane Installations by Manufacturer as of April 2000	23
8  Distribution of Installed Membrane Capacity by Manufacturer as of April 2000	24
9  Geographic Distribution of Membrane Installations in the United States	25
10 Distribution of Membrane Installations by State	26
11 Cumulative Number of Membrane Installations	27
12 Cumulative Membrane Capacity.	28
13 Summary of Virus Removal by MF/UF Process Classification	42
14 Maximum Log Removal Credits for Giardia and Cryptosporidium for 29 States	82
15 Maximum Virus Log Removal Credits for MF and UF for 29 States	82
16 MF/UF Integrity Monitoring Requirements for  29 States	83

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                                LIST OF ACRONYMS
AFT           Alternate filtration technology




ASDWA       Association of State Drinking Water Administrators




AWWA        American Water Works Association




AWWARF     American Water Works Association Research Foundation




CFE           Combined filter effluent




CIP           Clean-in-place




CPE           Comprehensive Performance Evaluation




CT            Disinfectant residual (mg/L) x contact time (minutes)




CWS          Community water system




DBP           Disinfection byproduct




DBPR         Disinfectant and Disinfection Byproducts Rule




DI            Deionized water




EPA           United States Environmental Protection Agency




ETV           Environmental Technology Verification




FACA         Federal Advisory Committee Act




FBR           Filter Backwash Rule




FR            Federal Register




FSR           Future  state requirement




GAC          Granular activated carbon




gfd            Gallons per square foot per day




GWUDI       Ground water under the direct influence (of surface water)




HAA          Haloacetic acid




HPC           Heterotrophic plate count
                                        VI

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ICR           Information Collection Rule




IESWTR       Interim Enhanced Surface Water Treatment Rule




IO             Inside-out




LNTU         Laser turbidimetry




LRAA         Locational running annual average




LT1ESWTR    Long Term 1 Enhanced Surface Water Treatment Rule




LT2ESWTR    Long Term 2 Enhanced Surface Water Treatment Rule




MCL          Maximum Contaminant Level




MCLG        Maximum Contaminant Level Goal




M-DBP        Microbial-Disinfection Byproducts




MF            Microfiltration




MGD          Million gallons per day




MIB           Methylisoborneol




MPA          Microscopic Particulate Analysis




MPN          Mean probable number




MRDL        Maximum Residual Disinfectant Level




MRDLG       Maximum Residual Disinfectant Level Goal




MWCO        Molecular weight cut-off




MWD         Metropolitan Water District (of Southern California)




NA            Not applicable




NF            Nanofiltration




NR            Not reported




NSF           National  Sanitation Foundation




NTNCWS      Nontransient noncommunity water system




NTU           Nephelometric turbidity units
                                       Vll

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OI




PAC




PC




pfu




PM




psi




PVDF




PWS




RO




SDWA




SR




SWTR




TC




TCU




THM




TMP




TOC




TSS




UF




UV




UV-254




WQ




WWTP
Outside-in




Powdered activated carbon




Particle counting




Plaque forming units




Particle monitoring




Pounds per square inch




Poly vinyl difluoride




Public water systems




Reverse osmosis




Safe Drinking Water Act




State requirement




Surface Water Treatment Rule




Total coliforms




True color units




Trihalomethane




Transmembrane pressure




Total organic carbon




Total suspended solids




Ultrafiltration




Ultraviolet (light)




Ultraviolet absorbance at 254 nm




Water  quality




Wastewater treatment plant
                                         Vlll

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EXECUTIVE SUMMARY
Microfiltration (MF) and ultrafiltration (UF) are low-pressure membrane filtration processes that
have gained considerable acceptance in the drinking water industry over the past ten years.  MF
and UF are primarily used  for particle removal  as  stand-alone treatment,  retrofit of existing
conventional treatment plants (as a replacement for conventional particle removal processes), or
as pretreatment to advanced processes such as nanofiltration (NF) and reverse osmosis (RO).
MF and UF have  been demonstrated to be  capable of removing  protozoa cysts  to  below
detection, as well as meeting the turbidity requirements of surface water treatment regulations.

The primary objective of this report is to summarize the current use and status of membrane
filtration technologies for drinking water applications  as well as the regulatory requirements that
govern  this technology.   Eight  membrane  equipment manufacturers,  29 State regulatory
agencies, and  24 utilities  were contacted to gather  information regarding  the growth of the
membrane  industry,  permitting requirements, and operation of MF/UF facilities in the United
States.

A utility may  choose to install membranes for a number of reasons; however,  the decision is
usually  influenced by existing, pending,  and/or anticipated regulatory requirements.   Concern
over microbial contaminants, independent of the regulations, is  another frequently cited  reason
for selecting membranes.  Other  drivers  for membrane technology include  ease of operation,
minimal staffing requirements, ability to  handle fluctuations in source water quality, and  cost
competitiveness of membrane technology with conventional processes.

The results from a  number  of challenge studies  have demonstrated that integral membrane
filtration systems can remove protozoan cysts  to below detection limits.  Removal of virus by
these  processes is more  variable and depends on membrane properties,  solution chemistry,  and
the formation  of a dynamic cake  layer on the membrane surface.  In general, UF membranes
have demonstrated greater virus removal  than  MF  membranes.  However, breaches in integrity
can compromise the removal capability of membrane filtration processes.  Thus, even though
intact membranes represent  an absolute barrier, it is necessary to verify the integrity of the
membrane system through routine  testing.

There are  two general types of integrity test methods, direct and indirect. Direct methods are
non-destructive techniques that are applied directly to  the membrane system to identify or isolate
breaches.   The  most commonly  applied  direct methods  are the pressure  hold test and the
diffusive air flow test.  Both methods are applied to  an  entire membrane  rack and can detect  a
very small  breach over several hundred thousand  fibers.  The primary disadvantage of current
direct methods is that they cannot be performed continuously while the system is in operation.
However, new innovations, such as continuous sonic  testing, may eventually  provide a reliable,
on-line method for directly monitoring membrane integrity.

Indirect methods are not applied  to  the physical  membrane system, but rather monitor some
aspect of filtrate water quality as a surrogate  measure of integrity.   Particle counting, particle
monitoring and turbidity monitoring are all used as forms of indirect integrity monitoring.  These
methods characterize potential integrity  problems by  a deviation in filtrate quality from an
                                          IX

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established baseline.  A primary advantage of indirect methods is that they can be applied in a
continuous, on-line mode. In addition, the instruments used for indirect testing can be applied to
any  membrane  system,  independent of manufacturer,  system  configuration,  or any  other
parameter intrinsic to a proprietary system.  Moreover, indirect methods  are likely to remain
applicable to  any new systems that are developed.   The disadvantage  of these monitoring
techniques is that they currently lack the sensitivity to detect small breaches that are of concern.

The demonstrated ability of membrane filtration processes to remove pathogens, and the ability
of integrity monitoring techniques to  demonstrate that  a membrane system is intact, are factors
considered  in the regulation  of these technologies.   Twenty-seven states  with operational
membrane facilities in the US have had to address these issues in order to develop a regulatory
approach  for  this  technology.    States  have had to  develop  these  approaches somewhat
independently  due  to the  absence  of federal  guidance, and  this  has  resulted in  variable
requirements for this technology.

State agencies have considered a variety of factors when determining removal credits, including
demonstration of treatment efficiency, total removal/inactivation requirements, experience with
the technology,  and  approach towards  multiple barrier treatment.   Although the results  of
microbial challenge studies demonstrate very high levels of removal, states rarely grant removal
credits in excess of the federal requirements for removal/inactivation of pathogens. Most states
contacted during this project grant between 2.5- and 3-log of Giardia removal credit for MF and
UF membranes.   Only seven states have awarded removal credit for  Cryptosporidium ranging
from 2- to 4-log. With only a few exceptions, states did not grant virus removal credits  to MF
processes, and in no case was the virus removal credit greater than 0.5-log.  Seven states have
awarded virus removal credit to membranes classified as UF processes, with credits up to the 4-
logs required under the Surface Water Treatment Rule (SWTR).

Regardless of the removal credits granted to a membrane  process, in almost all cases  states
required some level of chemical inactivation following  membrane filtration.  In cases where less
than the level  of treatment required by the SWTR was awarded, disinfection sufficient to make
up the balance of these  requirements is necessary.  However,  even in cases where complete
removal credit was granted to a  membrane filtration process, states  still required a minimum
level of chemical inactivation.

There were  also significant differences in the monitoring required by different states. Fourteen
of the 29 states did not require any integrity monitoring for MF/UF plants  aside from turbidity,
which typically lacks the sensitivity to detect small breaches in integrity that are of concern. Of
the remaining  15 states, 12  require physical  integrity  testing  with  or without continuous
monitoring and  one state requires only continuous testing.  All  states that require  periodic
physical integrity testing stipulate use  of the  pressure hold test, while states  that  require
continuous testing permit use of particle counting, particle monitoring, laser turbidimetry, or
pressure drop.

Integrity testing is a key component in a membrane filtration application, both from a regulatory
and a public health perspective.  However, both direct and indirect methods have limitations as
integrity testing  tools.  Pressure-driven tests are extremely sensitive and can verify integrity to

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very high levels; however, these methods are not continuous, and provide no measure of filtrate
water quality.  Indirect methods  are continuous and on-line, but cannot verify integrity to the
levels necessary to ensure high removal efficiency.  However, direct and indirect methods can
complement each other in a comprehensive monitoring program.  Seven of the states contacted
during this project do require a dual approach to integrity monitoring: periodic direct testing to
verify integrity to  a very  high level, and indirect monitoring to ensure that  a minimum level of
performance is achieved on a continuous basis.

The commonly used integrity tests provide information in the form of a response that is typically
used in  a relative manner  to  evaluate  whether or  not  system  performance is  acceptable.
However, the information that is of primary concern is the risk of microbial passage resulting
from an integrity breach.  It is possible to have an integrity breach that is sufficiently small such
that the  membrane process is  still  capable  of achieving  the  required  level of  removal.
Conversely, an insensitive monitoring technique may leave a critical integrity breach undetected.

In general, states have taken the approach that any integrity breach identified during monitoring
must be immediately  addressed, regardless  of the impact of the breach on  removal efficiency.
Although this practice is certainly justified from the standpoint of maintaining the integrity of the
treatment  barrier  and  providing superior public health  protection, it does not provide  any
indication regarding the severity of the breach as it relates to microbial passage. Integration of
the relationship between membrane  integrity and  microbial risk into the regulatory framework
would improve the constancy in which these tests are applied as well as the  interpretation of test
results.  This  approach would not eliminate the need  to address minor integrity breaches that are
identified  during routine monitoring, but would provide an indication of the impact of any breach
on  microbial removal efficiency,  and  better demonstrate  the  manner  in   which integrity
monitoring fits into the overall context of multiple barrier protection.
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1.0   INTRODUCTION
The Surface Water Treatment Rule (SWTR) was promulgated in 1989 to provide public health
protection against pathogens in surface water supplies.  This regulation includes combined filter
effluent turbidity standards, requires minimum levels of removal and/or inactivation for viruses
(4-log) and Giardia (3-log), and mandates filtration for all surface water systems unless strict
source water controls are met.  The Interim Enhanced Surface Water Treatment Rule (IESWTR),
promulgated in December 1998, establishes more stringent filtered water quality standards for
turbidity and sets a Maximum Contaminant Level Goal (MCLG) of zero for Cryptosporidium for
large systems (i.e., those serving more than 10,000 persons) utilizing filtration. The Long Term
1 ESWTR (LTIESWTR),  scheduled for promulgation in 2001, will extend the requirements of
the IESWTR to smaller systems  (serving fewer than 10,000 persons).

In September 2000, the Long Term 2 ESWTR (LT2ESWTR) Agreement in Principle was signed
by the United States Environmental Protection  Agency (EPA) and members of the Microbial-
Disinfection Byproducts  (M-DBP) Rule  Cluster Federal Advisory  Committee  Act  (FACA)
Committee (65 FR  83015).  The LT2ESWTR agreement includes source water quality-based
requirements  for up to  2.5-log inactivation  and/or  removal  of  Cryptosporidium  beyond
conventional treatment.

Conventional treatment has been proven effective for surface water treatment, and relies on the
combination  of coagulation, sedimentation,  and  filtration  processes  to  remove  microbial
contaminants through a variety of mechanisms (Patania,  et al.,  1995;  Lipp and Baldauf, 2000).
There  are also "barrier"  technologies  that achieve very  high  levels of pathogen  removal,
primarily  through  a  sieving   or  size  exclusion mechanism.    Microfiltration  (MF) and
ultrafiltration (UF) are two technologies that have consistently proven effective for the removal
of larger pathogens such as Giardia and Cryptosporidium.

The  SWTR  addresses conventional treatment  plants,  as  well  as  other media   filtration
technologies, such as direct filtration,  slow sand filtration, and  diatomaceous earth  filtration. All
other  filtration technologies are  addressed under the  alternate filtration technology  (AFT)
provision  of the SWTR.   Since the application of MF/UF to surface waters was still a novel
concept at the time the SWTR was developed, these processes are not specifically addressed in
the associated  guidance  (EPA, 1990).   Rather, these advanced  filtration technologies are
considered under the AFT provision of the SWTR,  which  does  not adequately address the
removal capabilities and specific requirements of MF and  UF.  As  a result,  state primacy
agencies have had to develop  an approach for permitting and regulating membrane  filtration
technologies.   Some states have elected to treat MF/UF as AFT, while others have  developed
requirements  specific to these technologies.  This  has resulted in a range of permitting practices
for membrane filtration applications in the United States.

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1.1   Purpose

The  LT2ESWTR  Agreement in  Principle proposes  greater than  2.5-log  Cryptosporidium
removal credit for membrane technologies  provided that specific performance criteria are met,
including demonstration of removal efficiency and adequate integrity testing.  However, there is
some disparity in  the current paradigm for demonstrating removal efficiency and performing
integrity  testing, which has implications for the regulation  of this technology.   This report
provides  a summary of these issues and will  be a useful resource for  regulators and utilities
considering membrane filtration for control of pathogens.  Specifically, this report is intended to:

1) Document the  ability of existing membrane filtration processes to remove microorganisms
   and surrogate parameters.

2) Summarize the advantages, disadvantages, and limitations associated with direct and indirect
   integrity test methods.

3) Identify the factors that affect integrity  monitoring methods, and  relate the impact of those
   factors to method sensitivity and microbial risk.

4) Summarize operational practices of existing membrane plants, including the drivers leading
   to the installation of membrane filtration, pretreatment processes employed, backwash and
   chemical cleaning practices, and integrity testing methods.

5) Describe the regulatory approaches used by state agencies to permit MF/UF  for pathogen
   removal during drinking water treatment, including demonstration of process performance,
   determination of removal credits, and integrity monitoring requirements.

1.2   Methodology

To achieve the objectives outlined above, a number of sources were contacted and the resulting
information summarized in this report.  The data sources and information targeted during this
project are  described in the following sections and summarized in Table 1.

1.2.1  NSF International

The  Environmental  Technology  Verification (ETV) program is a peer-reviewed certification
program  designed  to  facilitate  the  deployment  of innovative  or improved environmental
technologies through performance verification and dissemination of information.  One phase of
this  program involves  testing of membrane filtration for the removal  of  microbiological  and
particulate  contaminants.  The ETV protocol for membrane filtration includes an evaluation of
the removal of turbidity and particles,  as well as optional microbial  challenge studies.  The ETV
protocol also requires the  evaluation of the integrity  test used with a given membrane system.
Reports and supporting data from six NSF ETV studies were used during this project.

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Table 1.  Project Data Elements
     NSF International
     List of participating MF/UF systems
     Copies of  ETV  test reports,  including  all test and  operating  conditions,  water quality test
     parameters, 90th  percentile and maximum membrane pore size, testing  protocols,  results  of
     membrane integrity tests and surrogate monitoring, and results of microbial challenge studies
     MF/UF Equipment Suppliers
     Descriptions of MF/UF system configuration, membrane geometry, basic principles of operation,
     and backwashing and chemical cleaning methods employed
     Details of integrity test methods, including established criteria for determining pass/failure
     Results of manufacturer in-house tests (performance test data) and interpretation of test results
     Installation list and information  specific to  each installation  that  was  required  to obtain state
     approval	
     Utilities
     Description of treatment facilities,  source  waters, treatment objectives, disinfection strategies,
     and operational problems (i.e., system failures)
     Water quality data, including feed water  temperature, pH,  hardness,  alkalinity, turbidity, and
     particle counts
     Membrane  equipment supplier, design  and  typical  operating  ranges for  membrane  flux,
     transmembrane pressure, specific flux, feed water recovery, backwashing and chemical cleaning
     frequencies, and cleaning protocols and chemicals
     Results  of  bench- or pilot-scale tests,  including  seeding and challenge studies, as well as
     simulated system failures (i.e., cut fibers)
     Membrane integrity test methods, frequency, and test results
     Removal credits granted by state agencies	
     State Regulatory Agencies
     MF/UF pilot testing for state  approval  including any  re-testing requirements for subsequent
     locations and reciprocity allowances for testing conducted in other states
     The approach used by states to grant removal credits for membrane filtration processes
     Current  disinfection/removal  credits granted  to  MF/UF systems,  focusing on  Giardia,  but
     including data on other pathogens when available
     Any data or information a state  has regarding removal of microbial contaminants with MF/UF
     systems
     Integrity testing and other monitoring requirements
     List of operating or planned MF/UF systems in the state
     Strategy for dealing with MF/UF processes installed at different locations within a plant	

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1.2.2  MF/UF Equipment Suppliers

Eight MF and UF equipment suppliers (Aquasource, F.B. Leopold, Hydranautics, Ionics, Koch,
Pall, US Filter, and Zenon) were contacted to obtain descriptions of their membrane filtration
equipment as well as their installation lists.  These eight manufacturers were selected  since they
either have full-scale installations in the United States and/or have completed the ETV program.
These  suppliers were  asked to provide information regarding basic  principles of operation,
including details of integrity  test methods, results  of  in-house performance  studies, drinking
water  plant installation  lists, and  information or test results specifically required  by state
regulatory agencies.

1.2.3  Utilities

Utilities  that currently operate a MF/UF  facility, have piloted the technology  and are in the
process of constructing  a MF/UF plant,  or have  operated a  MF/UF  plant in the past were
contacted and asked to provide information regarding their operational experiences.  Each utility
was  asked to provide a description of the treatment facility, source water, treatment objectives,
disinfection  practices, integrity testing methods, and the  results of special studies  (either pilot-  or
full-scale) demonstrating microbial removal  capabilities  of the MF/UF membrane used.  Due  to
the substantial number of membrane filtration facilities located in the United States, a limited
number  of  membrane utilities  were  selected  to  represent  a cross-section  of states  and
manufacturers.  When possible, the first MF/UF plant permitted in a state was contacted since it
was  expected that the first  membrane plant would have been subjected  to the most rigorous
permitting requirements.

1.2.4  State Regulatory Agencies

Regulatory agencies in States in which one or more MF/UF facilities are  installed, or which have
established procedures for permitting membrane  filtration processes, were contacted to obtain
information   regarding their  permitting  process.   State  agencies  were  asked  to  provide
information  regarding pilot  testing  requirements,  removal  credits,  and integrity monitoring
requirements for permitting and operating a membrane filtration facility.

1.3   Report Overview

This report is divided into the following Chapters:

Chapter  1. Introduction:   Provides the basis  for the information contained in this report, the
purpose of the report, and the data collection methods used to achieve these objectives.

Chapter  2.  Background:  Presents a brief history  of  microbial and  surface water  treatment
regulations,  an overview of the application of MF/UF for compliance with these regulations, and
a summary of recent regulatory developments that make MF/UF a viable compliance option for
surface water systems facing Cryptosporidium removal requirements. Provides a brief overview
of the  basics of membrane filtration operation, as well as the use of MF and UF in the United
States.

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Chapter 3. Microbial Removal:   Documents the removal efficiency  of membrane  filtration
processes for microbial contaminants, including protozoa, bacteria, viruses, and surrogates.

Chapter 4. Integrity Testing:  Describes the integrity monitoring techniques commonly used in
membrane  filtration applications,  including the limitations, advantages,  and disadvantages of
each method.

Chapter  5.  Membrane  Integrity  and  Microbial Risk:   Discusses  factors  that  affect  the
performance, sensitivity,  and detection limit of integrity monitoring methods.  Relates the theory
of these methods to the impact of a detectable breach on membrane  performance and microbial
passage.

Chapter 6. Regulatory Approaches to Microfiltration and Ultrafiltration:  Discusses the approach
to regulating MF/UF by various state agencies.  Includes the initial evaluation of membrane
products, pilot testing requirements, log  removal credits granted,  and integrity  monitoring
requirements.

Chapter 7. Utility Practices:  Summarizes MF/UF operating practices reported by utilities located
throughout the United  States.   Includes  driving force  for  MF/UF  installation,  design and
operational considerations, and chemical cleaning and backwash practices.

Chapter 8.  Summary and Conclusions:  Summarizes the findings of this  project, including  the
ability of MF/UF to remove microbial contaminants, design and operational issues, permitting
requirements, and integrity testing and monitoring considerations.

Section 9.  References:   Lists  all literature used during  the preparation of this  report in a
bibliographic format.

Appendices:  Provides a comprehensive MF/UF installation list at the time of this report.

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2.0   BACKGROUND
2.1   Regulatory History

In 1990, the EPA  Science Advisory Board concluded that exposure to microbial contaminants
such as bacteria, viruses, and protozoa was likely the greatest remaining health risk management
challenge for drinking water suppliers (EPA, 2000a).  Acute health effects from exposure to
microbial pathogens  are well-documented,  and  associated illness can  range  from  mild to
moderate cases lasting only a few days to more severe infections that can last several weeks and
may result in death for those with weakened immune systems.

Between 1972 and 1981, 50 waterborne outbreaks of  Giardiasis occurred  nationwide involving
approximately 20,000 reported cases  (EPA,  1999a).  In 1993, an estimated 403,000 people
became ill, and  4,400 were  hospitalized during a Cry/?fosporidiosis  outbreak in Milwaukee,
Wisconsin. In 2000, an E. coli outbreak in Canada infected hundreds  of people  and may  have
been responsible for as many as seven deaths (AWWA, 2000).  The Safe Drinking Water Act
(SDWA)  provided the mandate for  the  EPA to  develop regulations to protect against such
waterborne pathogenic health threats.

Under the SDWA, as amended in 1986, EPA can establish a treatment technique requirement in
lieu  of a Maximum  Contaminant Level (MCL) for  those contaminants for which the agency
determines "it  is  not economically  or technically  feasible  to  ascertain the  level  of the
contaminant."  Pathogens are discrete microorganisms that typically occur at low levels in source
waters, and large sample volumes are necessary to ensure analysis of a representative sample.
The  presence of pathogens is not easily translated to viability  or infectivity, and therefore not
necessarily an indicator of public health risks (Allen,  et al., 2000).  Microbial  contamination is
often associated with a specific event,  such as high surface water runoff, and as a result, can be
difficult to detect using routine periodic monitoring.  Since measuring microbial contaminants in
drinking water  can be challenging  and expensive, EPA has established treatment technique
requirements for microbial contaminants.

Treatment requirements for  microbial contaminants  are  generally expressed in terms of log
removal  or log inactivation.  For example, the SWTR established treatment requirements of 3-
log and 4-log  removal/inactivation of  Giardia and viruses,  respectively.   The  efficacy of
membrane treatment is typically expressed in terms  of log removal, which is defined by the
following equation:


                               log removal = log:
                           Where:       C;n  = Feed concentration
                                         Cout = Filtrate concentration

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Since chemical  (and ultraviolet  light) disinfection methods kill or prevent  reproduction  of
microbial contaminants rather  than remove  them  from the finished water, control by these
methods is expressed as log inactivation.  Log inactivation is calculated in the  same manner  as
log removal,  only the finished water concentration is expressed in terms of the viability of the
remaining pathogens.

The log removal/inactivation concept is also easily translated to percent removal/inactivation.
For  example, 1-log  is equivalent to 90 percent,  2-log is equivalent to 99 percent,  3-log  is
equivalent to  99.9 percent, and so forth.

Public water  systems (PWSs)  that utilize surface water or ground water under the  direct
influence of surface  water (GWUDI) are typically  more vulnerable to microbial contamination.
Since 1989,  several regulations have  been developed  to  address this  potential  vulnerability,
including the Surface Water Treatment Rule, Interim Enhanced Surface Water Treatment Rule,
and the  Long Term 1 and Long Term 2 Enhanced Surface Water Treatment Rules.

MF and UF can be used to meet the turbidity and disinfection requirements of the surface water
treatment rules.  Both have demonstrated the ability to reduce turbidity to less than 0.1 NTU, and
are considered effective for the removal of Cryptosporidium and Giardia; furthermore, UF can
also be used for virus removal.  Chapter 3 discusses the removal capabilities of MF/UF in greater
detail. The following sections discuss the requirements of existing and proposed drinking water
regulations affecting surface water systems.

2.1.1  Surface  Water Treatment Rule

The SWTR was promulgated in June 1989 and applies to all PWSs that utilize surface water  or
GWUDI (54  FR 27486).  The SWTR includes treatment technique requirements for filtered and
unfiltered systems that are intended to  protect against the adverse health effects associated with
Giardia, viruses, and Legionella, as well as other pathogenic organisms.   Specifically, the
following requirements are included in the SWTR:

    1)  MCLGs of zero for Giardia, viruses and Legionella.

    2)  Requirements for maintenance of a disinfectant residual in the distribution system.

    3)  3-log  (99.9%) removal or inactivation of Giardia.

    4)  4-1 og  (99.99%) removal or inactivation of viruses.

    5)  Combined filter effluent turbidity performance standard of 5 NTU as a maximum and
       0.5  NTU at the 95th percentile  on a monthly basis, calculated using 4-hour monitoring
       data.  Applicable to treatment plants using conventional treatment.

    6)  Watershed protection and other requirements for unfiltered systems.

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2.1.2  Interim Enhanced Surface Water Treatment Rule

The  Interim Enhanced Surface Water Treatment Rule, finalized in December 1998,  applies to
PWSs serving 10,000 or more people that use surface water or GWUDI.  Affected systems must
comply with the requirements of the IESWTR by January 2002. The objectives of the IESWTR
are to improve control of microbial  pathogens, specifically the protozoan Cryptosporidium, and
address risk trade-offs between pathogens and disinfection byproducts (63 FR 69477).  Key
provisions established by the rule include:

   1)  MCLG of zero for Cryptosporidium.

   2)  2-log (99%) Cryptosporidium removal requirements for  systems that filter.  Systems that
       utilize  conventional or direct filtration are  credited with 2-log removal if they comply
       with the more stringent turbidity standards of the rule.

   3)  Reducing the combined filter effluent turbidity standard to 1.0 NTU as a maximum and
       0.3  NTU as the 95th percentile on  a  monthly  basis, calculated using 4-hour monitoring
       data. Applicable to treatment plants using conventional treatment or direct filtration.

   4)  Requirements for individual  filter turbidity monitoring.  All systems using surface water
       or GWUDI must continuously monitor turbidity from each filter and must provide  an
       exceptions  report to the state agency  on a monthly basis.  Exceptions include:  individual
       filter with a turbidity greater than 1.0 NTU based on two consecutive measurements  15
       minutes apart; and individual filter with turbidity level greater than 0.5 NTU at the end of
       the  first four hours of operation  based upon two consecutive measurements 15  minutes
       apart.   A self-assessment and filter profile  must be produced within seven days of the
       exception if no obvious reason for the exception can be identified.

       If an individual filter has turbidity levels greater than 2.0 NTU based on two consecutive
       samples taken 15 minutes apart, the  system must have a Comprehensive Performance
       Evaluation  (CPE) conducted  by the  state or a third party.

   5)  Microbial benchmarking/profiling provisions to assess the level of microbial  protection
       provided as PWSs take steps to comply with new disinfection byproduct standards. This
       is to prevent significant reductions in  microbial protection as systems modify disinfection
       practices to meet MCLs for trihalomethanes  (THMs) or haloacetic acids (HAAs).

   6)  Inclusion of Cryptosporidium in  the  definition of GWUDI and in the watershed control
       requirements  for unfiltered systems.  Any ground water determined to be  susceptible to
       Cryptosporidium is considered  GWUDI.  Any PWS using a watershed control program to
       avoid filtration must expand the program to include Cryptosporidium.

   7)  Requirement for covers on new finished water reservoirs.

   8)  States must conduct sanitary surveys for all surface water systems regardless of size at
       least once every three years.

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2.1.3  Long Term 1 Enhanced Surface Water Treatment Rule

The  Long Term  1  ESWTR, proposed in April 2000, is  designed  to  1) improve control of
microbial pathogens in drinking water, including Cryptosporidium,  for PWS serving fewer than
10,000 persons; and 2) prevent increases in microbial risk while PWS serving fewer than 10,000
modify treatment to comply with the Stage 1 D/DBP Rule (65 FR 19046).  The LT1ESWTR
extends the requirements of the IESWTR to systems serving fewer than 10,000 persons.

2.1.4  Filter Backwash Rule

The  purpose of the Filter Backwash Rule (FBR), also proposed in April 2000,  is to require
certain PWSs to institute changes to the return of recycle flows within the treatment process to
reduce the  potential effects of increased  microbial  concentrations in recycle  residuals  on
treatment plant performance (65 FR  19046).   The rule contains three basic provisions for
conventional and direct filtration plants that recycle and use surface water or GWUDI:

   1)  Recycle flows must be introduced prior to the point of primary coagulant  addition.

   2)  Systems employing 20 or fewer filters and recycling backwash to the treatment process
       must perform a one time  self-assessment of their recycle practice and consult with their
       primacy agency to address and correct high-risk recycle operations.

   3)  Systems utilizing direct filtration must report to the State on whether flow equalization or
       treatment is provided for recycle flows.

2.1.5  Long Term 2 Enhanced Surface Water Treatment Rule

In September 2000, an Agreement in Principle was reached by  EPA and members of the FACA
Committee regarding the requirements of the proposed LT2ESWTR.  The agreement contains
the following provisions  (65 FR 83015):

   1)  Systems serving more than 10,000  persons will be required to conduct Cryptosporidium,
       E.  coli.,  and turbidity source water monitoring on a  predetermined schedule for  24
       months.  Systems with historical data that is equivalent  in sample number and frequency
       may  use that data in lieu of new  monitoring at the discretion of the primacy agency.
       Systems that provide an additional  2.5-log removal/inactivation of Cryptosporidium (i.e.,
       2.5-log treatment beyond  conventional filtration) are exempt from monitoring.  The log
       removal/inactivation  determination will  be based upon  a framework of "microbial
       toolbox options" discussed below.

       EPA  and a panel of stakeholders will evaluate alternative indicators, such as E.  coli, for
       predicting Cryptosporidium occurrence in systems serving fewer than 10,000 persons. If
       an alternative surrogate cannot be identified, small systems will begin one year of E. coli
       monitoring two years after large systems initiate  Cryptosporidium monitoring.  Small
       systems  will be required to conduct Cryptosporidium monitoring if annual average E. coli
       concentrations exceed 10/100 mL for lakes and reservoirs or  50/100 mL for streams.
                                         10

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2) Based upon  monitoring results,  systems will  be classified  in  four  "bins."  The bin
   determination will specify what additional level  of treatment for  Cryptosporidium   is
   required beyond conventional treatment.  Table 2  summarizes  the  bin requirements
   outlined in the September 2000 agreement.
Table 2. LT2ESWTR Bin Requirements
Bin
Number
1
2
3
4
Average Cryptosporidium
Concentration
< 0.075 cysts/L
> 0.075 to < 1 .0 cysts/L
> 1 .0 to < 3.0 cysts/L
>3.0
Additional Treatment Requirements for Systems with
Conventional Treatment and in Full Compliance with IESWTR
No action.
1-log treatment (systems may use any technology or combination of
technologies from microbial toolbox provided total credit is at least 1-
log)
2-log treatment (systems must achieve at least 1-log of the required
2-log treatment using ozone, chlorine dioxide, UV, membranes,
bag/cartridge filters, or in-bank filtration)
2.5-log treatment (systems must achieve at least 1-log of the required
2.5-log treatment using ozone, chlorine dioxide, UV, membranes,
bag/cartridge filters, or in-bank filtration)
3) The requirements of an action bin may necessitate that a PWS take one or more actions to
   meet  the additional treatment levels.   EPA  and the FACA Committee  developed  a
   "toolbox" approach that would allow a PWS to choose from a number of alternatives to
   meet   the  requirements  of  the  rule.     The   microbial   toolbox   options   and
   removal/inactivation credits outlined in the Agreement in Principle are shown in Table 3.

4) Unfiltered systems will be required to continue to meet the filtration avoidance criteria,
   and  provide  4-log   virus   inactivation,   3-log   Giardia  inactivation,   and  2-log
   Cryptosporidium inactivation.   Disinfection requirements must be met using a minimum
   of two disinfectants.

5) Systems using uncovered finished water reservoirs will be required to install a cover,
   unless the system installs treatment to achieve a 4-log virus inactivation or the  state
   agency determines existing risk mitigation is adequate.
                                      11

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Table 3. LT2ESWTR Microbial Toolbox Components*

Potential Log Credit
0.5
1
2
>2.5
Watershed Control
Watershed Control Program (1)
Reduction in oocyst concentration (3)
Reduction in viable oocyst concentration (3)
X



As measured
As measured
Alternative Source
Intake Relocation (3)
Change to Alternative Source of Supply (3)
Management of Intake to Reduce Capture of Oocysts in Source Water (3)
Managing Timing of Withdrawal (3)
Managing Level of Withdrawal in Water Column (3)
As measured
As measured
As measured
As measured
As measured
Pretreatment
Off-Stream Raw Water Storage w/ Detention ~ X days (1)
Off-Stream Raw Water Storage w/ Detention ~ Y weeks (1 )
Pre-Settling Basin w/Coagulant
Lime Softening (1)
In-Bank Filtration (1)
X

X _



X
	 *
— *
X









— >
Improved Treatment
Lower Finished Water Turbidity (0.15 NTU 95% tile CFE)
Slow Sand Filters (1)
Roughing Filter (1)
Membranes (MF, UF, NF, RO) (1)
Bag Filters (1)
Cartridge Filters (1)
X

X -









X









X

X
^

X
^


Improved Disinfection
Chlorine Dioxide (2)
Ozone (2)
UV(2)
X
X

X
X


X



X
Peer Review / Other Demonstration / Validation or System Performance
Peer Review Program (ex. Partnership Phase IV)
Performance studies demonstrating reliable specific log removals for
technologies not listed above. This provision does not supercede other
inactivation requirements.

X


As demonstrated
* As outlined in the September 2000 Agreement in Principle (65 FR 83015). The removal credits identified in this table are based
  upon the September 2000 Agreement in Principle and are subject to change. The final LT2ESWTR (anticipated in May 2002) will
  include the final toolbox components and identify design and operational criteria necessary to receive log removal credit.

Key to table symbols: (X) indicates potential log credit based on proper design and implementation in accordance with EPA
guidance. Arrow indicates estimation of potential log credit based on site specific or technology specific demonstration of
performance.

Table footnotes: (1) Criteria to be specified in guidance to determine allowed credit,  (2) Inactivation dependent on dose and source
water characteristics, (3) Additional monitoring  for Cryptosporidium  after this action would determine  new bin classification and
whether additional treatment is required.
                                                     12

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2.1.6  Stage 1 Disinfectants and Disinfection Byproducts Rule

Although MF and UF do not remove disinfection byproduct (DBF) precursors, they can reduce
distribution system  DBF formation  by reducing the disinfectant  dose  required to meet  the
disinfection/removal requirements  of the surface water treatment rules.  The Disinfectants and
Disinfection Byproducts Rule (DBPR) will be promulgated in two stages.  Stage 1 of the DBPR
applies to all PWSs that are community water systems (CWSs) or nontransient noncommunity
water systems (NTNCWS) and which use a chemical disinfectant for either primary or residual
disinfection. Surface water and GWUDI systems serving at least 10,000 people are required to
comply with the DBPR by January  2002.   All groundwater systems (regardless of size), and
surface water and GWUDI systems  serving fewer than  10,000 persons must comply  with  the
Stage 1 DBPR by January  2004.   The Stage 1 DBPR includes  the following provisions (63  FR
69389):

1) Maximum Residual Disinfectant Level Goals (MRDLGs) for chlorine (4 mg/L), chloramines
   (4 mg/L) and chlorine dioxide (0.8 mg/L).

2) MCLGs for  four  THMs: chloroform  (0  mg/L),  bromodichloromethane  (0  mg/L),
   dibromochloromethane  (0.06 mg/L), and bromoform (0 mg/L).

   MCLGs for two HAAs: dichloroacetic acid (0 mg/L) and trichloroacetic acid (0.3 mg/L).

   MCLGs for bromate (0  mg/L) and chlorite (0.8 mg/L).

3) Maximum Residual Disinfectant Levels (MRDLs) for three  disinfectants: chlorine (4 mg/L),
   chloramines (4 mg/L) and chlorine dioxide (0.8 mg/L).

4) MCLs for total  trihalomethanes (TTHMs) (0.08  mg/L),  the  sum of  five haloacetic  acids
   (HAAS) (0.06 mg/L), bromate (0.01 mg/L) and chlorite (1.0  mg/L).

5) Systems utilizing surface water or GWUDI and using conventional filtration are required to
   remove specified percentages of organic material (measured as total organic carbon - TOC).
   TOC removal  will  be achieved primarily through enhanced coagulation  or enhanced
   softening. Table 4 summarizes the TOC removal requirements.

   Table 4. Required TOC Removal by Enhanced Coagulation and Enhanced Softening
Source Water TOC
(mg/L)
>2. 0-4.0
>4.0-8.0
>8.0
Source Water Alkalinity (mg/L as CaCO3)
0-60
35.0%
45.0%
50.0%
>60-120
25.0%
35.0%
40.0%
>120
15.0%
25.0%
30.0%
   Source: National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts; Final Rule (63 FR 69389)

The rule also provides a number of alternatives to meet the enhanced coagulation requirement as
described in the final rule (63 FR 69389).
                                         13

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2.1.7  Stage 2 Disinfectants and Disinfection Byproducts Rule

The Stage 2 DBPR, which will be proposed along with the LT2ESWTR in mid-2001, will apply
to all CWSs and NTNCWSs that add a disinfectant other than UV or deliver disinfected water.
Compliance will be based on  a  locational  running  annual  average  at  monitoring  locations
throughout the distribution system.  This compliance framework is intended to control spatial
peaks in the distribution system.  The Stage 2 M-DBP Agreement in Principle (65 FR 83015)
outlines the following provisions:

Systems must comply with the Stage 2 DBPR in two phases.   In Phase I, systems must comply
with a  locational running  annual average (LRAA)  of 120 and  100 |ig/L for TTHM and HAAS,
respectively, at each Stage 1 DBPR monitoring location. Additionally,  systems must continue to
meet the Stage 1 DBPR running annual averages for TTHM and HAAS during Phase I.  Systems
must comply with Phase  I within three  years of rule promulgation, which  is anticipated to be
mid-2002.

During Phase II, which begins  six years after rule promulgation, systems will need to comply
with a LRAA  of 80  and 60 |ig/L for TTHM and HAAS,  respectively,  at  new monitoring
locations selected during an initial distribution system evaluation.  These new monitoring points
will  include  locations that  are  representative  of long residence  times  and  high DBF
concentrations.
                                         14

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2.2   Membrane Filtration

2.2.1   Overview of Low-Pressure Membrane Filtration

Membranes act as selective barriers, allowing some constituents to pass through the membrane
while blocking the passage of others.  The movement of material across a membrane requires a
driving force (i.e., a potential difference  across the membrane), and the  membrane processes
commonly used in drinking water applications use pressure as the driving force.  There are four
categories of pressure-driven membrane processes: microfiltration, ultrafiltration, nanofiltration
(NF), and reverse osmosis (RO). RO and NF processes are typically applied for the removal of
dissolved constituents including both inorganic and organic  compounds,  and  these processes
operate at pressures significantly higher than MF  and UF.  Low-pressure membrane processes
(i.e.,  MF and  UF)  are  typically applied  for  the  removal  of  paniculate  and microbial
contaminants, and can be operated under positive pressure or negative pressure (i.e., vacuum
pressure).  Positive pressure systems typically operate between 3 and 40 psi, whereas, vacuum
systems operate between -3 to -12 psi. There is no significant difference  between the range of
pressures at which MF and UF systems operate.

In the membrane process industry, the distinction between  MF and UF is typically based upon
the molecular weight cut-off (MWCO) or pore size. MWCO is a manufacturer specification that
refers to the molecular mass of a macrosolute (e.g. glycol or protein)  for which a membrane has
a retention capability of greater than 90  percent (\nselme and  Jacobs, 1996).   The pore size
refers the diameter of the  micropores in a membrane surface.   It is difficult to measure the true
pore size, and as a result membrane manufacturers typically  use some measure of performance to
categorize the pore size of a membrane.  The nominal pore size is typically based upon a given
percent removal of a marker (e.g., microspheres) of a known diameter. The absolute pore size is
often  (though not always) characterized as the largest pore size in a membrane surface.  That is,
the absolute pore size is the minimum diameter above which 100 percent of a marker of a
specific size is  removed by a membrane.  Figure 1 presents  the MWCO/pore size ranges for
membrane process, as well as the relative size of some common drinking water contaminants.

Although  pore size is an  important consideration  in  determining which  contaminants  a
membrane process can remove, it  is not the only factor that impacts removal. The relevancy of
pore  size  to  membrane performance  is  limited by the lack of a  standard methodology for
characterizing and reporting the pore size  of different membrane products.  Furthermore, factors
other  than pore size  can impact performance, such as the build up of a cake layer on a membrane
surface over the course of a filtration cycle.  For this reason, membrane rejection characteristics
are often assessed through challenge  studies in which the ability  of a membrane to reject a
specific contaminant is demonstrated.  In  this manner, the actual exclusion characteristic of the
membrane is empirically determined and accounts for all of the factors that impact performance.
The exclusion characteristic is a direct measure of performance and thus can be used to compare
two different membranes,  whereas the pore size is an indirect measure of rejection capability and
may not be an appropriate metric for comparison.
                                         15

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     100
  1000 10,000
100,000  500,000
                                                            APPROXIMATE MOLECULAR WEIGHT
       !         I    I            !'
         0.001 M     0.01 M      0.1 M
                                           10M
                                    100M
1000M
I           I
   Dissolved Organics


              Viruses
                                               Bacteria
                                                                    !            I
                                                                         Sand
                                                                    i
          Salts
                            Colloids
                                                          Cysts
                                   Media Filtration
                                  I	L
                                          J  Microfiltration
                   i     r
                         I Ultrafiltration
                     Nanofi It ration

               Reverse Osmosis
 Figure 1.  Membrane Process Classification

MF and UF membranes are made from a wide variety of materials, including:  polypropylene,
polyvinyl difluoride (PVDF), polysulfone, polyethersulfone and cellulose acetate.  The various
membrane  materials  have different properties, including pH and  oxidant  sensitivity, surface
charge, and hydrophobicity.  These material characteristics can affect the exclusion characteristic
of a membrane as well as operating constraints such as the potential use of pre-chlorination to
control biological fouling.

All commercially available MF and UF membranes currently used for drinking water treatment
are constructed in a hollow fiber configuration.  Hollow fiber membranes are operated in either
an inside-out or outside-in mode. During inside-out operation, the feed enters the fiber lumen
and passes through the fiber wall to generate filtrate. During outside-in  operation, the filtrate is
collected in the fiber lumen after the feed is passed through the membrane.  A cross section of a
fiber is shown below in Figure 2.
                       Figure 2.  Photomicrograph of a Hollow Fiber

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Another characteristic that can affect the performance of hollow fiber membranes is the trans-
wall symmetry.  Two constructions are commonly used in MF/UF membrane: asymmetric and
composite.  In asymmetric construction, the membrane material is homogeneous throughout the
membrane cross-section; however, the  density of the membrane decreases from the feed to the
filtrate side of the membrane.  Composite membranes are constructed by casting a thin, dense
membrane skin onto the surface of a porous  substructure. The thin film is always cast onto the
feed side of the membrane, but in some cases, is cast onto both sides to provide additional
mechanical strength and to allow bi-directional filtration. Figure 3  presents schematics of both
symmetric and composite membranes.
     DOC5OO
      GOO
         Asymmetric fiber
Top layer
(dense or porous)

Porous
substructure
                                                                        •d— Dense skin
Porous
substructure
                        Composite fiber
Figure 3.  Schematic of Asymmetric and Composite Membranes

Typically, membrane fibers are bundled in groups of several thousand, potted in a resin on both
ends, and housed in a pressure vessel, or module. When operated in an inside-out mode, the feed
water enters the lumen at one or both of the potted ends of the vessel. In the outside-in mode, the
feed water typically  enters the center of the pressure vessel and is forced into the lumen.  There
are also submersible membrane  systems in which the fibers are immersed in a tank containing
the feed water, open to the atmosphere, and vacuum pressure is applied to filtrate side of the
membrane. Figure 4 shows a typical hollow-fiber membrane module configuration.
                                 Permeate
              Feed
                                                                    Concentrate
                    Hollow fibers
        \    Perforated sleeve
        Potting resin
   Figure 4. Typical Hollow Fiber Module Configuration (Aptel and Buckley, 1996)

Membrane processes are designed using one or more water production units, typically referred to
as racks or skids.  A rack consists of a number of modules, or cartridges, which share common
                                         17

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feed and filtrate valving.  Typically, individual membrane racks can be isolated from the rest of
the system for testing, cleaning or repair.

The major  components of a typical MF or UF membrane  system include cartridge filters  or
strainers for  removal  of large  debris,  low pressure  feed pumps, membrane  modules, high-
pressure backwash pumps, a chemical cleaning system, a chlorine feed system, and a concentrate
handling and disposal system.

Membrane  modules may  also be operated  using either a cross-flow or dead-end flow pattern.
With  a dead  end flow pattern,  all of the  feed water passes through the membrane, trapping
particles on the membrane surface until  backwashing or chemical cleaning removes them.  In a
cross-flow mode, the feed water flows tangential to the membrane surface, which is intended to
enhance productivity by limiting the extent of particle deposition and cake layer formation on the
membrane  surface.  In order to  achieve a significant scour velocity  at an acceptable product
water recovery during cross-flow  operation,  it is necessary  to recirculate a  portion of the
concentrate, which  requires additional pumping and  thus can  substantially increase operating
costs.  Figure 5 presents a graphical representation of the  differences in the two operational
configurations.
Filter [
Cake
Cake L
p p pr
ry EL. O" n" JT P"_Q" FT P" P rr
P" O^T Q" CT U D"^ ^D" D" M-* rP^ r^ F~*J
^ Filtrate »
Cross-flow configuration
Feed Flow
/^gp^>p f"
| I
T Filtrate
Dead-end configuration
Concentrate
Stream
. Membrane
^—Membrane
       Figure 5. Schematic of Membrane Flow Configurations

Typical process  monitoring in  a membrane treatment process  includes  flow,  pressure,
temperature, and turbidity, all of which can be monitored continuously.  The data collected can
be used to monitor system performance and generate production reports.  In addition, membrane

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filtration systems rely on periodic integrity testing to check for breaches. The types of integrity
testing most commonly used are discussed in greater detail in Chapter 4.

The membrane filtration process may be designed to operate using positive pressure or negative
pressure (i.e., vacuum pressure) as the driving force.  The pressure that is used to drive water
through the membrane is termed transmembrane pressure (TMP).  In a positive pressure process
the feed water  is pressurized  and fed to membranes  typically  housed  in  pressure vessels.
Immersed membrane systems are not housed in a pressure vessel, and thus cannot be pressurized.
Instead, the membranes  are placed in a basin  containing  the  feed water and the filtrate is
collected in the fiber lumens by applying a partial vacuum on the filtrate side.

One  of the critical  design parameters for a membrane process  is flux,  which is typically
expressed in gallons  of filtrate per day per  square foot of membrane area (gfd). The preferred
method for determining design flux is through pilot testing, but in the absence of pilot data, other
water quality data  and manufacturer information may  be used to estimate this parameter.  The
design flux determines the membrane area required for a specific plant capacity.  Thus, flux has a
significant impact on capital cost, and results in a competitive motivation for design engineers to
use a higher membrane flux, thereby reducing the area requirements. Although, increasing the
membrane flux  can  reduce the  capital cost, it will  increase operational  costs due to higher
operating pressure, more  frequent chemical  cleaning,  and  a potential  increase  membrane
replacement costs.   Many  equipment manufacturers  and design engineers target a cleaning
interval of 30 days  or greater  to  minimize the amount of operator involvement and system
downtime to maintain acceptable productivity, as well  as minimize the costs associated with
chemical cleaning  and cleaning residuals disposal. However, an analysis of total  system costs
must be conducted to understand the cost implications of various cleaning intervals.

Another important  design parameter is recovery, the ratio of feed water to filtrate.  Recovery for
MF/UF systems is typically  85 to 97 percent.  High-pressure membrane systems typically
operate at significantly lower recoveries (70 to 90 percent).  In a membrane  filtration system,
recovery is typically  a function of the frequency of the backwash  and the method of backwash
disposal.  That is,  more frequent backwashing will typically result in lower recoveries.  Some
states may allow recycling of backwash water to the treatment process,  which can improve
recovery rates.

Backwashing of membranes is accomplished using air, water, or a combination of both.  Some
membrane processes also use chlorinated water to enhance the effectiveness of the backwash
process.  MF and UF processes are backwashed more frequently than  conventional filters.  A
typical range of backwash frequencies for MF/UF systems is between 15  and 60 minutes, and the
backwash duration ranges from 30 seconds to 3 minutes.  Ideally, the backwash process restores
the TMP  to the same  value following each backwash.  However,  most systems  experience a
gradual increase  in post-backwash TMP that must be addressed by chemical cleaning.

Chemical cleaning  is  used to restore the post-backwash TMP to its initial level, i.e., the TMP of a
new,  clean  membrane.  In  the chemical  cleaning  process,  acid, caustic,  chlorine, and/or
surfactants are circulated through the membrane system to dissolve or dislodge contaminants that
have not been removed by backwashing.  The  spent cleaning solution is then  flushed from the
                                          19

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system and neutralized prior to disposal.  Requirements for membrane system cleaning vary with
the type of membrane.   Some systems use a  chemically  enhanced backwash instead  of a
dedicated chemical cleaning  approach;  however, most systems, are chemically  cleaned  once
every one to six months,  depending on system design and operation.  Irreversible membrane
fouling is a loss of productivity that cannot be restored through chemical cleaning. Irreversible
fouling occurs in all membrane systems, and eventually requires the membranes to be replaced.

Suspended solids and other contaminants  can  result in more rapid fouling of the membrane,
decreases in flux, and increases in TMP. As a  result, most membrane filtration systems include
some level of  pretreatment to reduce  the concentration  of these  foulants, with the level of
pretreatment dependent upon raw water quality.

Water temperature  can also impact the membrane flux due to the increase in water viscosity with
decreasing temperature.  The viscosity of water affects the rate at which water travels through the
membrane pore structure.  As the viscocity increases at lower temperatures,  a greater TMP is
required  to maintain the target flux, resulting in increased operating costs.  Table 5 presents an
approximation of the effect of water temperature on water viscosity, as well as a correction factor
for membrane flux (Karimi, et al.,  1999).  This effect can vary from membrane to membrane,
and many manufacturers have developed membrane-specific correction factors.

            Table 5. Effect of Water Temperature on Flux
Temperature
°c m
25 (77)
20 (68)
15(59)
10(50)
5(41)
0.1 (32)
Viscosity
(cp)
0.891
1.00
1.15
1.30
1.55
1.79
Viscosity Correction
Factor
0.89
1.00
1.13
1.27
1.43
1.61
Thus, in the design of a membrane  treatment facility, a design water temperature range is
normally established.  The effect of viscosity on water production is generally considered to be
complementary, as most facilities have lower production demands when the water is cold,  i.e.,
during the winter.  However, if the facility is required to meet full design capacity under cold
water conditions, additional membrane surface area will be required.

MF  and UF membrane  treatment  processes are effective for the removal  of particles  and
microorganisms, as discussed in Chapter 3.  However,  these treatment processes are generally
not effective for removing dissolved materials present in water sources, including TOC, arsenic,
color, or undesirable taste and odor compounds, such as methylisoborneol  (MIB) and geosmin.
Removal of these contaminants will typically require a chemical or physical treatment process in
addition  to  membrane  filtration.   Removal  of TOC,  DBF precursors and  color  causing
                                         20

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compounds may be achieved through coagulation prior to membrane filtration.  Coagulation with
ferric salts followed by MF/UF has been  shown  to be a viable method to remove arsenic
(Chwirka, et al., 2000).  Some UF  membrane processes may be used with powdered activated
carbon to absorb taste and odor compounds (Jack and Clark, 1999).

2.2.2  The Use of Microfiltration and Ultrafiltration in the United States

Stricter regulations and concerns over waterborne disease outbreaks resulting from inadequate
treatment have lead water utilities to seek alternative technologies,  such as membrane treatment,
to ensure safe drinking water.   In  some  situations,  membrane processes  have the potential to
provide increased assurance of safe drinking water since microbial contaminants are completely
removed via a physical barrier.

MF and UF are  low-pressure filtration processes, which have gained considerable acceptance in
the drinking water industry over the past  ten years, and have demonstrated excellent capabilities
for removal of  pathogens  (see Chapter  3).   MF and UF  are primarily installed either as  a
replacement for clarification/filtration  or filtration in a conventional treatment process,  or as
pretreatment for processes such  as NF and RO.  Typically, MF and UF systems do not require
any pretreatment beyond straining,  although this may not be the case in all instances.  In  some
cases, particularly  with inside-out configurations, MF/UF must be preceded by clarification to
operate effectively.

A list  of 120  drinking water treatment facilities in  the United  States that utilize MF/UF was
developed from  installation lists provided by the following manufacturers: US Filter,  Zenon,
Aquasource, Pall, and Koch.  These manufacturers accounted for all of the MF/UF installations
in the  United  States at the time of this  report.  However, a number of other manufacturers,
including Ionics, Hydranautics,  Leopold, and Smith & Loveless  produce MF/UF  membranes
and/or process equipment.

The  comprehensive installation list  is based  on  current  full-scale  facilities,  pilot-  and
demonstration-scale plants,  and planned future facilities.  Only one facility, a pilot plant in New
Rochelle, New York, is no longer  in operation.  Of the remaining 119 installations, there are
currently  108  full-scale facilities  on-line.   The remainder  of the  facilities  are planned for
installation in 2001, most of which  conducted pilot  studies or constructed  demonstration plants.
Eighty-seven (73 percent) of the  facilities  utilize MF technology.

The  subsequent  analysis of the utility  information includes only the current full-scale facilities
unless  otherwise noted.  The information includes the type of membrane process, manufacturer,
treatment capacity, source water type, geographic distribution, and year of installation.

2.2.2.1   Treatment Capacity

The  treatment capacities of the membrane  plants in operation at the time of this report are
organized into five categories in Figure 6. The mean capacity for all installations is  1.71 MOD,
and  the  median is  0.36 MGD.   The median is significantly less then  the  mean  due to the
predominance of small  facilities. More than half of the MF/UF installations provide a treatment
                                          21

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capacity  less than 0.5 MOD.   Some of the reasons that MF/UF is an attractive  small system
technology  include:  ease of  operation,  excellent finished water  quality, high  degree  of
automation that reduces the need for continual  staffing, and modular design that does not require
custom engineering.  The largest operating facility is located in the City of Kenosha, Wisconsin.
The 14 MGD MF plant began operation in October 1998.
      40
   O
   •-P
|

—
ta
   -Q
   |

   I
      35 '
      30
      25
      20 '
      15 '
      10
                34
                               28
                                               24
                                                               15
              0-0.1           0.1-0.5           0.5-2            2-5             >5

                                   Treatment Capacity (MGD)

   Figure 6.  Distribution of Installed Membrane Treatment Capacity as of April 2000

There are also several large installations that are planned in the  near future.  The Olivenhain
Municipal Water District in California has a  25 MGD UF  facility under construction that is
planned for start-up in 2001.  The City of Westminster, Colorado has a 15 MGD MF facility
planned for start-up in June  2001.   A  20 MGD MF facility is  under construction for  the
Pittsburgh Water and Sewer Authority and is scheduled to be on-line in 2001.  Construction is
near completion in the City of Appleton, Wisconsin on a 24 MGD UF facility  scheduled for
start-up in the spring of 2001.  Minneapolis, Minnesota is planning a 70 MGD facility for start-
up in 2004, and Carmicheal, California is planning a 15 MGD  facility.  Bakersfield, California
and the Otay Water Treatment Plant in  San Diego, California are planning 20 and  40 MGD
facilities, respectively.  Finally, Del Rio, Texas is currently planning a 16 MGD facility.
                                          22

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2.2.2.2 Source Water

MF/UF processes  can be used to remove particles and pathogens from surface waters and
GWUDI.  The types of sources used by membrane filtration plants identified during this project
include: reservoirs, lakes, rivers, surface water impoundments, and aquifers under the influence
of surface water.

2.2.2.3 Manufacturer

Figure 7 presents the  distribution of membrane installations among the major manufacturers.
The  manufacturer with  the  largest number of membrane installations for  drinking  water
treatment is US Filter with nearly a 70 percent share of the market. Koch has the largest number
of new facilities, increasing its current number of installations by more than 50%, from 9 to 14
between 2000 and 2001.   Two large Pall facilities are scheduled for installation in 2001: a 30
MOD  facility  in  Westminster,  Colorado facility and  a  20 MOD facility  in Pittsburgh,
Pennsylvania.
80 -
70 -
a 60 "
o
a
E 40 -
o
Number
U)
0
1
20 -
10 -






12
n


75













7
             Aquasource        Koch           Pall          US Filter

                                          Manufacturers
Zenon
    Figure 7. Distribution of Membrane Installations by Manufacturer as of April 2000

Figure 8 presents the distribution of installed capacity by manufacturer. Again, US Filter has the
largest percentage  of installed capacity in the United  States at 48 percent.  However, installed
capacity is more evenly distributed among the five leading manufacturers than is the number of
installations.  Pall currently has 19 percent of the market, followed by Zenon at 16 percent, Koch
at 10 percent, and Aquasource at 6 percent.  The difference in percent of market share by number
                                          23

-------
of installations compared to installed capacity is largely the result of increased use of MF/UF
technology in the United States, as well as the increased capacity of new installations. US Filter
(Memcor) dominated the early market and installed a number of small facilities. As the use of
membranes has increased, the number of large installations has also increased which has allowed
the share of installed capacity to grow disproportionate to the number of installations.
       100 1
Q'
O
        90-
        80-
    -s   70
    '0
    oa
    §•  60
    U
A
I   401
    I   30-
£   20-

    10-
         0
                  12
                                                               92
                                                36
                                 19
                                                                              31
              Aquasource
                            Koch            Pall          US Filter

                                       Manufacturer
Zenon
  Figure 8. Distribution of Installed Membrane Capacity by Manufacturer as of April 2000

2.2.2.4 Geographic Location

The geographic distribution of existing membrane installations is shown by region in Figure 9
and by state in Figure 10.  The figures  do not include future installations, as reported by the
manufacturers.  The states with existing  or planned membrane facilities were grouped into five
regions for the purpose of this summary:

   •   West region - Alaska,  Hawaii, California, Oregon, and Washington

   •   Mountain region - Arizona, Colorado, Idaho, Nevada, Utah, and Wyoming

   •   Midwest region - Michigan, Kansas, Missouri, Oklahoma, South Dakota and Wisconsin

   •   South region - Florida, North Carolina, Tennessee, and Texas
                                         24

-------
    •   Northeast region - Connecticut, Massachusetts, New York, New Jersey,  Pennsylvania,
       and Virginia.

The West region has the largest number of MF/UF facilities in the United States with 40 percent
of the total number of installations.  Two new installations are planned for the coming year in the
Western region.  The Northeast region is second  with 20 percent of the  existing installations.
Growth in the Midwest region is highest  with four new facilities planned.  The Mountain and
Southern regions each have two new facilities planned.

The reasons for the  dominance of the West and Northeast regions are the disproportionately high
number  of installations  in California and Virginia,  respectively.    California  alone has
approximately 25 percent of the total installations in the United States, and Virginia accounts for
more than 10 percent of the installations.

As  experience  grows,  more  states  are expected to  accept  membranes and award appropriate
removal credits. Consequently, the use of MF/UF technology is expected to continue to grow  in
the  United  States.   Existing and future regulations make  membranes an attractive treatment
option, for reasons discussed throughout this report.
     a
     o
o
•_
.c
E
3
Z
        50  -•
        40  -•
        30  -'
        20  -•
        10  -•
                  46
                                 20
                                                                             22
                                                13
                West        Mountain        Midwest         South

                                       Geographic Locations
                                                                      Northeast
   Figure 9. Geographic Distribution of Membrane Installations in the United States
                                          25

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30

25 f

20

15 •-

10 •-

 5 •-
        11
                                                              12
              n
_    3            _         33
ll,n,n,ll,A,n,n,ll,n,n,n,n,n,n,n,n,l

                                                                .n.n.n
   AK AZ CA CO CT FL  ffl ID  KS MA MI MO NC  NJ NV NY OK OR PA SD TN TX UT VA WA WI WY
                                  States
Figure 10. Distribution of Membrane Installations by State

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2.2.2.5 Installation Trends and Treatment Capacity

Membrane filtration  first  entered  the drinking water  treatment  market  in  1987  with the
installation of a 0.06 MGD system at Keystone Resorts in Keystone, Colorado.  Since then, the
number of installations has steadily risen. Figure 11 shows the cumulative number of membrane
installations corresponding to installation year.  In the first six years of MF/UF installations, 30
membrane facilities, about one-quarter  of the current facilities, were installed, while 83 facilities
were installed in the past five years.

The cumulative treatment capacities of the on-line facilities as of April 2000 are  shown in Figure
12. In the first six years,  the cumulative treatment capacities were very low, less than 3 MGD.
Since 1996, the cumulative treatment capacity  has  risen from approximately  7 MGD for 28
facilities to nearly 190 MGD for 110  facilities (an  increase in the  average plant capacity from
0.25 MGD to 1.7 MGD).   Additionally, there is 54 MGD of future treatment capacity planned
with the addition of 10 new facilities, and these numbers do not include potential facilities  in
Minneapolis (70 MGD), San Diego (40  MGD), and Carmichael (15  MGD),  which were not
included in the future installations list provided by the manufacturers.
    140
    120
  a
A  80
"S
•_

"a  60
3
Z
5  40
O
H
                                                                                   120
                                                                              110
                                                                         92
                                                                    63
                                                              47
                                                         28
                                                    21
1
             1
                    1
1
        1987  1988  1989  1990  1991  1992  1993  1994  1995  1996  1997  1998  1999  2000  2001

                                        Installation Year

                      * Projected based upon manufacturer provided information.
Figure 11. Cumulative Number of Membrane Installations
                                          27

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     300
     250 -
  Q

  O
  8"
1
~s

 s
U
     200 -
     150 -
     100 -
      50-
                                                                                            243
                                                                                       189
                                                                                 122
                                                                           61
                                                                     31
          0.06   0.06   0.06  0.06   0.09   0.11
                                             3.9
                                                    4.2
                                                         4.7
                                                               7.0
          1987   1988   1989  1990  1991   1992   1993   1994   1995   1996   1997  1998  1999  2000  2001


                                            Installation Year




                      * Projected based upon manufacturer provided information.
Figure 12. Cumulative Membrane Capacity
                                              28

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3.0   MICROBIAL REMOVAL
3.1    Introduction

This section summarizes the results of a number of microbial and particle challenge studies that
demonstrate the ability of MF/UF membranes to achieve up to 7-log removal of pathogens and
particles. However, these results must be evaluated in the  context of the study design.  MF and
UF are barrier technologies,  and an integral membrane system  will remove any particle  (or
pathogen) that is  larger than  the exclusion characteristic of the membrane system.   Since  log
removal is a function of the influent contaminant concentration, the removal efficiencies reported
for challenge studies  are a  function  of the initial  concentration  as  well as  membrane
performance.  When organisms or particles are  removed  to  below the detection limit,  the
reported log removal is limited by the influent concentration.

Seeded challenge  studies are often performed to assess microbial removal.  Typically, organism
stock solutions are batched by adding live organisms to a small  tank of dechlorinated water.
This organism stock solution is continuously pumped to  the membrane feed water.  Samples  are
collected from the  membrane feed water  (post-organism  addition) and  from the filtrate  to
measure removal  through the membrane system.  Recycle streams  and waste streams are also
frequently sampled to perform a mass balance on the organisms. Samples are collected in sterile
bottles, stored at the required temperature, and tested within  the maximum holding time.  These
samples can be taken at various times  during a filtration cycle to  demonstrate either 'best-case'
or 'worst-case' membrane removal conditions.  For example, a membrane might best be able to
remove particles and/or pathogens smaller than  its pore size towards the end of a filtration cycle
after a cake layer  on the membrane surface has formed  and  matured. Conversely, a membrane
might  be least able to remove such particles and/or pathogens immediately after a  chemical
cleaning event due to the lack of a cake layer on the membrane surface.

Seeded challenge studies  must often  be performed to adequately assess membrane removal
efficiencies for specific organisms since concentrations of certain organisms  (e.g.,  Giardia and
Cryptosporidiuni)  in many natural waters are frequently too low to be accurately measured. That
is,  naturally  occurring concentrations of these  organisms are  generally  not sufficient  for
challenge studies that attempt to test the limits  of treatment  capabilities. As evidence of this, a
statistical summary  of the  Giardia and Cryptosporidium monitoring results  of the Information
Collection Rule (ICR) are presented in Table 6.

The need for seeded challenge studies  is compounded by the efficacy of the  analytical methods
used (Allen, et al., 2000).   EPA conducted spiking studies  to determine  the recovery of the ICR
Giardia and Cryptosporidium analytical  methods (EPA,  1995).   Results  of those studies
indicated the average recoveries were 12 percent for Cryptosporidium and 26 percent for Giardia
(EPA,  2001). Recoveries of Giardia and Cryptosporidium are typically much higher in seeded
challenge studies.  It is worth noting that EPA has since issued improved analytical methods for
the detection of Cryptosporidium and Giardia (EPA, 1999b and 1999c).
                                         29

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   Table 6. ICR Monitoring - Giardia and Cryptosporidium Occurrence Summary
Parameter
Minimum (per 100 ml)
Maximum (per 100 ml)
Average (per 1 00 ml)
50tn percentile (per 100 ml)
75tn percentile (per 100 ml)
95in percentile (per 100 ml)
Number of samples with detectable protozoa1
Number of non-detect samples '
Cryptosporidium
1
1923
97
34
82
413
401
5438
Giardia
1
2521
141
54
156
568
1107
4732
    1 - Minimum, maximum, average, and percentiles do not include samples in which protozoa were not detected. Statistics are
      based solely on those samples in which Cryptosporidium or Giardiawere detected.

The removal of microorganisms by  a membrane is dependent on a number of factors, one  of
which is the formation of a dynamic cake layer on the membrane surface.  This cake layer will
typically improve removal efficiencies for some pathogens over the filter cycle (Jacangelo, et al.,
1995).  Particles can be physically removed (sieving)  by the cake layer, or may be adsorbed  to
particles in the cake layer. This phenomenon makes it difficult to compare results from different
challenge studies, because the researchers  do not generally account for the cake layer in the
results  presented,  and it is often unclear whether  the results were  obtained using a  clean
membrane (early in the  filtration cycle) or a fouled  membrane (near  the end of the filtration
cycle).

This  section presents the results of  various  studies  evaluating the  efficacy of membrane
technology for the  removal of microbial and surrogate parameters.  Specifically, it  evaluates
MF/UF for the removal of  protozoa,  bacteria,  viruses, turbidity and particles,  and  other
organisms.

3.2   Protozoan Cysts

Protozoan cysts, which include the regulated pathogens Giardia and Cryptosporidium, are  some
of the larger microbial  contaminants of concern.  Giardia and  Cryptosporidium cysts  have
diameters approximately  one to two  orders of magnitude greater than typical MF nominal pore
diameters (0.1 to 0.5 urn) and two to three-and-a-half orders of magnitude  greater than typical
UF nominal pore diameters  (0.005 to 0.05 |im).  The primary removal mechanism  for cysts  is
sieving  which typically results in removal to detection limits when the  membrane system is not
compromised.

Results  of Giardia and Cryptosporidium challenge testing are summarized  in Tables 7 and  8,
respectively.  All studies were performed through seeding of the feed water.   As seen  in both
Tables  7  and  8, for most studies cysts  were removed to below  the detection limit, thus the
calculated log removal by MF  and UF processes for Giardia and Cryptosporidium cysts was a
function of influent organism concentration.  This is expected since these cysts are larger than
the absolute pore size of the MF and  UF membranes tested. However, a breach in integrity, such
as a broken fiber or a ruptured seal, can result in passage of cysts to the filtrate.  As an example,
during  one  study cysts  were  found in the treated water at levels  above  the  detection  limit
                                          30

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(Jacangelo, et al., 1997).  In this case, the researchers identified a defective seal on the membrane
module of the pilot unit as the breach in integrity.

Tables 7 and 8  also demonstrate that Giardia and Cryptosporidium removal efficiency is not a
function of membrane configuration, pore size or membrane material, for the studies considered
in this report. In addition, a variety of source water types, including wastewater treatment plant
(WWTP)  effluent, seeded deionized (DI) water,  and surface waters, were used in the studies
without influencing cyst removal efficiency. Several researchers reported pore size in units of
MWCO.  An approximate conversion scale for MWCO to |im is presented in Section 2.2, Figure
1.
                                          31

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Table 7. MF and UF Studies Documenting Giardia Removal Efficiency
Researcher
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
MWD report, Coffey
NSF
Year
1997
1997
1997
1997
1997
1997
1997
1997
1993
1993
1993
1993
1992
2000b
Process
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
Water Source
surface water
surface water
surface water
surface water
surface water
seeded Dl water
seeded Dl water
seeded Dl water
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
surface water
treated surface water
Log Removal
>6.4*
>6.9*
>6.9*
>7.0*
>6.7*
>4.7* to >5.2*
>4.7* to >5.2*
>4.6+to>5.0*
4.99
5.76
7.33
6.6*
>4.4*
>5.8*

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Table 7. MF and UF Studies Documenting Giardia Removal Efficiency (continued)
Researcher
Olivieri, et al.
Schneider, et al.
Schneider, et al.
Schneider, et al.
Trussel, et al.
Vickers, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Dwyer et al.
Year
1987
1999
1999
1999
1998
1993
1997
1997
1997
1997
1997
1997
1997
1997
1995
Process
MF
MF
MF
MF
MF
MF
UF
UF
UF
UF
UF
UF
UF
UF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
NR
Pore Size
0.2 |jm
0.2 |jm
0.1 |jm
0.1 |jm
0.2 |jm
0.2 |jm
300,000 MWCO
500,000 MWCO
100,000 MWCO
500,000 MWCO
100,000 MWCO
500,000 MWCO
100,000 MWCO
100, 000 MWCO
100,000 MWCO
Water Source
NR
filter backwash
filter backwash
filter backwash
tertiary wastewater
effluent
surface and
groundwaters
seeded Dl water
seeded Dl water
seeded Dl water
surface water
surface water
surface water
surface water
surface water
seeded Dl
Log Removal
5.6
>4.8
>4.8
>4.8
>5.1*
4 to >6.4*
>5.0*
>5.0* to >5.2*
>4.7* to >5.2*
>6.4*
>7.0*
>6.7*
>6.7*
>6.9*
>5*
                                 33

-------
              Table 7. MF and UF Studies Documenting Giardia Removal Efficiency (continued)
Researcher
Hagen
Jacangelo, et al.
Jacangelo, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
NSF
NSF
NSF
NSF
Trussel, et al.
Year
1998
1989
1991
1993
1993
1993
2000e
2000a
2000c
2000d
1998
Process
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
1 00,000 MWCO
1 00,000 MWCO
100,000 MWCO
0.05 |jm
0.01 |jm
0.02 |jm
100, 000 MWCO
100, 000 MWCO
0.01 |jm
0.03 |jm
100,000 MWCO
Water Source
surface water
surface water
surface water
WWTP effluent
WWTP effluent
WWTP effluent
treated surface water
treated surface water
treated surface water
treated surface water
tertiary wastewater
effluent
Log Removal
>i.r
>5*
>4
7.31
7.39
7.26*
>6.6* to >6.8*
>5.5*
>4.9*
>5.3*
>5.1*
* indicates removed below detection limit.
+ indicates a broken seal.
++ indicates a potentially contaminated filtrate tank or line.
NR - Not reported.
                                                      34

-------
Table 8. MF and UF Studies Documenting Cryptosporidium Removal Efficiency
Researcher
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
NSF
Olivieri, et al.
Schneider, et al.
Schneider, et al.
Schneider, et al.
Trussel, et al.
Jacangelo, et al.
Year
1997
1997
1997
1997
1997
1997
1997
1997
1993
1993
1993
1993
2000b
1989
1999
1999
1999
1998
1997
Process
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
0.1 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
0.2 |jm
0.2 |jm
0.1 |jm
0.1 |jm
0.2 |jm
500,000 MWCO
Water Source
seeded Dl water
surface water
surface water
surface water
surface water
surface water
seeded Dl water
seeded Dl water
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
treated surface water
NR???
filter backwash
filter backwash
filter backwash
tertiary wastewater
effluent
seeded Dl water
Log Removal
4.2+ to >4.8*
>6.9*
>6.8*
>6.1*
>6.3*
>6.0*
>4.4* to >4.9*
>4.4* to >4.9*
4.86
5.74
>7.29*
>6.4*
>6.8*
4.8
4.2
>4.2
>4.2
>4.7*
>4.8* to >4.9*
                                35

-------
         Table 8. MF and UF Studies Documenting Cryptosporidium Removal Efficiency (continued)
Researcher
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Dwyer, et al.
Hagen
Jacangelo, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
NSF
NSF
NSF
NSF
Trussel, et al.
Year
1997
1997
1997
1997
1997
1997
1997
1995
1998
1989
1993
1993
1993
2000e
2000a
2000c
2000d
1998
Process
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
NR
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
300,000 MWCO
1 00,000 MWCO
500,000 MWCO
100, 000 MWCO
500,000 MWCO
100, 000 MWCO
100, 000 MWCO
100,000 MWCO
100, 000 MWCO
100,000 MWCO
0.05 |jm
0.01 |jm
0.02 |jm
100, 000 MWCO
100,000 MWCO
0.01 |jm
0.03 |jm
100, 000 MWCO
Water Source
seeded Dl water
seeded Dl water
surface water
surface water
surface water
surface water
surface water
seeded Dl
surface water
surface water
WWTP effluent
WWTP effluent
WWTP effluent
treated surface water
treated surface water
treated surface water
treated surface water
tertiary wastewater
effluent
Log Removal
>4.8*
>4.4* to >4.9*
>6.9*
>6.7*
>7.0*
>6.4*
>6.3*
>5*
>8*
>5*
6.89
6.99
>7.07*
>5.4* to >6.3*
>6.5*
>5.8*
>6.4*
>5.1*
+ Indicates a broken seal.
++ Indicates a potentially contaminated filtrate tank or line.
NR - Not reported.
                                                      36

-------
3.3  Bacteria

The biological category of bacteria encompasses many different microbial species.  As a result,
there exists a large range of shapes and sizes within this category; species range from spherical to
almost thread-like in shape and 0.1 jim to 100 urn in size (AWWA, 1999).  However, in general
most species of bacteria are larger than the exclusion characteristics of common MF and UF
membranes.  As with protozoan cysts, bacteria are primarily removed by MF/UF membranes
through sieving. However, filtration through the membrane cake layer  and adsorption onto the
cake layer may also play  a  role  in  the  removal  of  bacteria.   The combination  of these
mechanisms results in significant removal of bacteria by MF and UF systems.

Results of bacterial challenge testing are summarized in Table 9. Although many different types
of specific bacteria exist, general indicators of bacterial  contamination,  such as  total  coliforms
(TC) or Heterotrophic Plate Count (HPC), were used in most of the studies listed in this table.

The results in Table 9 show that for many of the  studies, bacteria were removed to below the
detection limit. Thus, the calculated log removal by MF  and UF processes was a function of the
influent organism concentration.  In many cases this is expected since the bacteria are larger than
the absolute pore size of the MF and UF membranes tested. However, a breach in integrity, such
as a broken fiber or a ruptured  seal, can result in passage  of bacteria to the filtrate. Note that the
reported log removals were  lower and varied  more widely for the bacterial tests than for the
protozoan studies.   This is because  many of the bacterial tests were conducted using naturally
occurring  bacterial concentrations, as opposed to  the seeded  challenge studies conducted for
protozoa.  Ambient concentrations are much  lower and more varied (e.g., 102 to 103 organisms
per L) than seeded  study influent  concentrations which can  be on the order of 105  or 106
organisms per L.

Unless aseptic practices are implemented, it is impossible in a plant environment to  maintain
sterile  conditions for "filtrate-side" components of a MF or UF system (e.g., filtrate piping  or
storage tanks). As a result, the potential for bacterial regrowth and contamination of the product
water downstream  of the membrane barrier exists even though the membrane process may have
removed all bacteria from the source water.   Bacteria, unlike protozoan cysts  and viruses, can
propagate without a host organism.  Contamination  can occur through a number of  routes,
including  the  presence of  airborne organisms and  human  contact with  the treated  water
components.   The potential for bacterial regrowth can be minimized through the use of a
disinfectant, such as chlorine, or by chemically cleaning the filtrate side of the membrane.
                                          37

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Table 9.  MF and UF Studies Documenting Bacteria Removal Efficiency
Researcher
Parker, et al.
Parker, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
MWD report,
Coffey
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Olivieri, et al.
Wilinghan, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
Kachalsky, et al.
Olivieri, et al.
Olivieri, et al.
Kachalsky, et al.
Year
1999
1999
1997
1997
1997
1997
1992
1997
1997
1997
1997
1991
1992
1993
1993
1993
1993
1991
1991
1993
Process
MF
MF
MF
MF
MF
MF
MF
UF
UF
UF
UF
MF
MF
MF
MF
MF
MF
MF
MF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
0.2 |jm
O.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
0.2 |jm
100,OOOMWCO
500,000 MWCO
300,000 MWCO
100, 000 MWCO
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.05 |jm
0.2 |jm
0.2 |jm
0.05 |jm
Bacteria Type
HPC bacteria
Total coliform
E. Coli
E. Coli
E. Coli
E. Coli
E. coli
E. Coli
E. Coli
E. Coli
E. Coli
Enterococci
Enterococci
Fecal coliform
Fecal coliform
Fecal coliform
Fecal coliform
Fecal coliform
Fecal coliform
Fecal coliform
Water Source
Filter backwash
Filter backwash
surface water
seeded Dl water
seeded Dl water
seeded Dl water
surface water
surface water
seeded Dl water
seeded Dl water
seeded Dl water
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
WWTP effluent
Log Removal**
3.3
>4.3
>7.8*
>7.8*
>7.8*
>7.8*
>6.0* to >6.4*
>7.8*
>9.0*
5.6 to 6. 9
>7.8*
>2.5*
2 to 4
1.39
2.83
2.83
4.02
>4.5*
>7*
1.80
                            38

-------
Table 9. MF and UF Studies Documenting Bacteria Removal Efficiency (continued)
Researcher
Kachalsky, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Clair, et al.
Clair, et al.
Luitweiler
MWD report,
Coffey
NSF
Vickers, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Henegan, et al.
Henegan, et al.
Jacangelo, et al.
NSF
Year
1993
1997
1997
1997
1997
1996
1997
1991
1992
2000b
1993
1997
1997
1997
1997
1991
1991
1989
2000g
Process
UF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
UF
UF
UF
UF
UF
UF
UF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot

Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
0.02 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
-
0.2 |jm
0.1 |jm
0.2 |jm
500,000 MWCO
100,OOOMWCO
500,000 MWCO
100, 000 MWCO
100, 000 MWCO
100, 000 MWCO
100, 000 MWCO
150,000-
180,000 MWCO
Bacteria Type
Fecal coliform
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
HPC
Water Source
WWTP effluent
surface water
surface water
surface water
NR
surface water
NR
NR
surface water
treated surface
water
surface and
groundwaters
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treated surface
water
Log Removal**
2.18
>1.7
>2.6
>2.1
>1.8*
0.5 to 2.4
2.4
1.7
0.4 to 2.2
0.2to0.4++
1.2 to 2.2
>1.7
>1.8
>2.1
>2.5
3.6 to 4
>3.4
2.8
1.9 to 2.3
                                  39

-------
Table 9. MF and UF Studies Documenting Bacteria Removal Efficiency (continued)
Researcher
NSF
NSF
NSF
NSF
NSF
Glucina, et al.
Hofman, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Olivieri, et al.
Olivieri, et al.
Vickers, et al.
Wilinghan, et al.
Year
2000a
2000e
2000c
2000d
2000f
1997
1998
1997
1997
1997
1997
1997
1997
1997
1991
1991
1993
1992
Process
UF
UF
UF
UF
UF
MF
MF
MF
MF
MF
MF
MF
UF
UF
MF
MF
MF
MF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
1 00,000 MWCO
1 00,000 MWCO
0.01 |jm
0.03 |jm
0.03 |jm
0.2 |jm
150, 000 to
200,000 MWCO
100,000 MWCO
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
500,000 MWCO
100,000 MWCO
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
Bacteria Type
HPC
HPC
HPC
HPC
HPC
HPC and total
coliforms
HPC, coliforms,
thermo-tolerant
coliforms, SSRC
P. Aeruginosa
P. Aeruginosa
P. aeruginosa
P. aeruginosa
P. aeruginosa
P. aeruginosa
P. aeruginosa
Total coliform
Total coliform
Total coliform
Total coliform
Water Source
treated surface
water
surface water
treated surface
water
treated surface
water
surface water
NR
surface water
seeded Dl water
seeded Dl water
seeded Dl water
seeded Dl water
seeded Dl water
seeded Dl water
seeded Dl water
WWTP effluent
Surface water
surface and
groundwaters
WWTP effluent
Log Removal**
1.2 to 1.8
0 to 0.2++
0.5
1.2 to 1.7
2.1 to 2.2
>3
2. 5 to 3. 5
>8.7*
>8.2*
>8.2*
>8.2*
>8.2*
>8.2*
>8.7*
>5.5*
Below detection
limit
1*->2.5*
2 to 6
                                  40

-------
                             Table 9. MF and UF Studies Documenting Bacteria Removal Efficiency (continued)
Researcher
Henegan, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Clair, et al.
Clair, et al.
Kothari, et al.
MWD report, Coffey
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Glucina, et al.
Jacangelo, et al.
NSF
NSF
NSF
NSF
Year
1991
1997
1997
1997
1997
1997
1996
1997
1992
1997
1997
1997
1997
1997
1997
1991
2000a
2000g
2000e
2000f
Process
UF
MF
MF
MF
MF
MF
MF
MF
MF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
100,OOOMWCO
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
1 00,000 MWCO
500,000 MWCO
100,000 MWCO
500,000 MWCO
100, 000 MWCO
100,000 MWCO
NR
100,000 MWCO
150,000-
180,000 MWCO
100,000 MWCO
0.03 |jm
Bacteria Type
Total coliform
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Total coliforms
Water Source
Surface water
NR
surface water
surface water
surface water
NR
surface water
surface water
surface water
NR
surface water
surface water
surface water
surface water
NR
NR
treated surface
water
treated surface
water
surface water
surface water
Log Removal**
2* to 3*
>1.8*
>1.7*
>3.0*
>1.9*
>3
Below detection
limit
Below detection
limit
>0.8* to 2.0*
>2.1*
>0.8*
>2.1*
>1.7*
>2.2*
>3
>3
>1.2*to>1.8*
>0.8*
>0.9*to>1.4*
>0.7*to 1.2*
' Indicates removal below detection limit.
** If value does not indicate removal below detection limit, the reference
  necessarily indicate that there were organisms detected in the filtrate.
+ Indicates a broken seal.
++ Indicates a potentially contaminated filtrate tank or line.
NR - Not reported.
which the value was taken from did  not state removal  below detection limit.  However, this does not
                                                                        41

-------
3.4  Viruses
The category of viruses also comprises a large group of organisms.  Viruses are much smaller
than protozoan cysts and bacteria.  Generally, virus sizes (i.e., 0.005 to 0.1 jim) compare to the
entire range of UF and the lower end of MF pore sizes.  There are a number of mechanisms by
which  viruses are removed by  membranes, including physical  sieving,  adsorption onto  the
membrane, filtration through  and adsorption onto particles in the cake layer,  and sieving as a
result of constriction of the membrane pores due to irreversible fouling (Jacangelo, et al., 1995).
Reported virus removal by MF and UF membranes has varied widely, which is expected since
many viruses are smaller than the pore sizes of MF membranes and comparable to the pore sizes
of UF  membranes.  UF membranes have exhibited virus removal to detection limits, while MF
membranes  often exhibit lower  removal, and, in  some cases, do not remove viruses to  any
appreciable  extent.  This distinction between MF and UF performance is a function of the
membrane exclusion characteristic, and not  the MF or UF classification used by the membrane
supplier. In practical  terms, the  difference  between MF and UF can be characterized by their
ability to remove viruses; UF acts as a physical barrier to viruses, MF does not.
Results  of virus testing are summarized in Table 10.
than 0.5-log) to below detection limits (i.e., > 6.5-log),
efficiencies  for virus by MF and  UF  systems.  For
MWCO (or -0.01  urn) or tighter, Table 10 shows
detection limits.  However, for membranes with pore
MWCO, viruses were less often removed to detection
capabilities, as reported in the studies cited in Table 10,
 Removals vary from marginal (i.e., less
 demonstrating the wide range in removal
 membranes with pore sizes of 100,000
that viruses were frequently reduced  to
sizes greater than approximately 100,000
 limits.  Figure 13 presents virus removal
 by MF or UF classification.
         10
      o
      o.
      o
      E
      &B
      O
      J
      E
      a
      E
      H
      OS
                                 MF
   UF
    Figure 13. Summary of Virus Removal by MF/UF Processes Classification
                                         42

-------
Some studies demonstrate that the elapsed operating time after a backwash or chemical cleaning
event may significantly impact virus removal (Jacangelo, et al., 1995). This is likely due to the
formation of a cake layer on the membrane surface. As the cake layer thickens and compresses
over the course of a filtration cycle, the ability of the membranes to remove viruses is improved.

The  age of a membrane can also impact virus removal.  Pore constriction may occur as a result
of irreversible fouling of a membrane, reducing the pore size and improving virus removal.  The
extent of pore constriction is a function of feed water quality (i.e., concentration of the foulant)
and membrane age.

Viruses may adsorb onto the membrane surface or larger particles in the feed water, which are
more effectively removed by the membrane.  Thus, water quality  parameters such as turbidity or
particle counts, may have an impact on virus removal. As evidence, the studies cited in Table 10
that were conducted with seeded DI water generally show less efficient virus removal than those
studies conducted using natural waters containing significant levels of particles.

The  majority of the results presented in Table 10 are based upon MS2 bacteriophage removal.
MS2 is commonly used as an indicator for virus removal because it is similar in size (0.025 |j,m),
shape, and nucleic acid makeup to poliovirus and hepatitis virus (Valegard, et al.,  1990).
                                          43

-------
Table 10.  MF and UF Studies Documenting Virus Removal Efficiency
Researcher
Parker, et al.
Parker, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Kruithof, et al.
MWD report, Coffey
Olivieri, et al.
Olivieri, et al.
Schneider, et al.
Schneider, et al.
Schneider, et al.
Trussel.et al.
Wilinghan, et al.
Jacangelo, et al.
Year
1999
1999
1997
1997
1997
1997
1997
1997
1997
1992
1991
1991
1999
1999
1999
1998
1992
1997
Process
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
MF
UF
Test
Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Demons
tration
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
0.2 |jm
0.2 |jm
0.2 |jm
0.2 |jm
0.1 |jm
0.2 |jm
0.2 pm
0.1 |jm
NR
0.2 |jm
0.2 |jm
0.2|jm
0.2 |jm
0.1 |jm
0.1 |jm
0.2 |jm
0.2 |jm
100,000
MWCO
Virus Type
Male specific
coliphage
Total culturable
virus
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
Human
enterovirus
Male specific
virus
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
Male specific
MS2
bacteriophage
Feed
Concentration
35200 perl 00 ml_
83,405 perl 00 L
NR
NR
NR
NR
NR
NR
1.0x103to3.5x103
pfu/ml
1. 3x1 0B to 3. 0x10'
pfu/ml

1.6x10 'to 1.6x10"
#/ml
NR
NR
NR
2.1x10'to2.6x10B
pfu/ml
3.0x10 'to 3.0x104
#/ml
NR
Water Source
Filter backwash
Filter backwash
surface and ground
waters
surface and ground
waters
surface and ground
waters
seeded Dl water
seeded Dl water
seeded Dl water
surface water
surface water
WWTP effluent
WWTP effluent
filter backwash
filter backwash
filter backwash
tertiary wastewater
effluent
WWTP effluent
surface and ground
waters
Log Removal
3.7
2.8
0 to 1.7
0 to 2.4
0 to 2.2
0.2 ± 0.3
1.2± 0.7
0.3 ± 0.4
0.7 to 2.3
1.65-2.87
2-6
1.3* to 4.3*
0.5
1.1
2.3
0.4 to 3.2
0.3 to 4*
>6.0to>7.9
                           44

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                  Table 10.  MF and UF Studies Documenting Virus Removal Efficiency (continued)
Researcher
Jacangelo, et al.
Jacangelo, et al.
Jacangelo, et al.
Dwyer, et al.
Dwyer, et al.
Dwyer, et al.
Jacangelo, et al.
Kruithof, et al.
NSF
NSF
NSF
NSF
NSF
NSF
Trussel, et al.
Year
1997
1997
1997
1994
1994
1994
1991
1997
2000e
2000e
2000f
2000f
2000g
2000g
1998
Process
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
UF
Test
Scale
Pilot
Pilot
Pilot
NR
NR
NR
Pilot
Demons
tration
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
500,000
MWCO
500,000
MWCO
100,000
MWCO
100,000
MWCO
10,000
MWCO
500,000
MWCO
100,000
MWCO
NR
100,000
MWCO
100,000
MWCO
0.03 pm
0.03 pm
150,000-
180,000
MWCO
150,000-
180,000
MWCO
100,000
MWCO
Virus Type
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
MS2
bacteriophage
Feed
Concentration
NR
NR
NR
2.43x10' to
3.12x108pfu/ml
2.43x1 07 pfu/ml
6.55x1 08 pfu/ml
1.0x10'to1.0x10B
pfu/ml
2.2x104to2.5x104
pfu/ml
7.4x10*to2.8x107
pfu/ml
3.5x10'to6.0x10'
pfu/ml
3.5x10Bto5.9x10B
pfu/ml
2.4x10Bto4.8x10B
pfu/ml
2.8x107to1.7x108
pfu/ml
4.5x107to1.1x108
pfu/ml
2.2x1 05 to 1.1x105
pfu/ml
Water Source
surface and ground
waters
seeded Dl water
seeded Dl water
seeded Dl
seeded Dl
seeded Dl
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
tertiary wastewater
effluent
Log Removal
0 to 1.4
1.5+ 0.4
>6.8*+ 0.3
1.0to6.5
6.2 to 6. 8*
1.5to6
>6.5to>7.0
>5.4
4.0 to 5.7
2.9 to 4.3
>5.5*to5.8
1.7to2.1
3.9 to 4.7
3.4 to 4.3
>6.9*
* indicates removed below detection limit.
+ indicates a broken seal.
++ indicates a potentially contaminated filtrate tank or line.
NR - Not reported.
                                                           45

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3.5  Algae

Protozoan cysts, bacteria, and viruses represent the  three groups  of pathogens currently of
concern to the water treatment industry for the protection of public health.  Algae are also of
concern to many water treatment facilities  since the chemical  byproducts  they produce can
impart an unpleasant taste and odor to water (AWWA, 1999). Algae are larger than the typical
pore size of MF  and UF systems, and  Table 11 presents several ETV  studies that  have
documented the  removal of algae  through MF and UF  processes.  In nearly all cases,  algae
counts were  reduced to below the detection  limit of 8  cells/ml.   Although  MF and UF
membranes have been demonstrate  capable of removing algae to detection limits, these processes
may not remove their byproducts.

3.6  Surrogate Challenge Parameters

Using Cryptosporidium or Giardia for the purpose of conducting challenge studies can be cost
prohibitive.  However, there are a  number of potentially suitable biotic and  abiotic surrogates
that could be used to assess the ability of a  membrane to remove Cryptosporidium.  Some of
these surrogates include  Pseudomonas,  Serratia,  Bacillus, polystyrene microspheres, and
endospores.  At the time of this report, little information was available regarding the performance
of MF and UF with respect to these surrogates.  As such, it is  difficult  to draw a conclusion
regarding the appropriateness  of these parameters as an indicator of membrane performance and
Cryptosporidium  removal.   However, they  have  been  identified  as  surrogates for  other
technologies (AWWA, 1999).

Another biological surrogate parameter that may be  used to assess membrane performance is a
Microscopic Particulate Analysis (MPA).   A MPA is  primarily used to assess the removal of
larger microorganisms, including bacteria and protozoa, and is only applicable to relatively clean
drinking  water sources.  In a MPA test,  the  filtered  water is analyzed  using polarized light
microscopy.  The analyst then looks for particles that may be microorganisms. If  organisms are
found, further testing may be performed to determine specific organism type.   The MPA is
seldom used due to the time and complexity of the procedure, and at the time of this report there
was no data to demonstrate that MPA had been used as an indicator of membrane performance.
It has, however, been used as an indicator for  other technologies (Schulmeyer, 1995).

Although  biological surrogates  can  provide a less costly  alternative to the use  of certain
microorganisms  for  challenge  studies, their measurement still  requires  substantial technical
expertise.  Consequently, the  removal capability of a membrane system is frequently monitored
through the  use  of non-biological  surrogate parameters.   These parameters  primarily include
polystyrene microspheres and particle count  measurements.  Microspheres have not been used
extensively to evaluate  membrane performance; however, they have been used  to assess the
performance of other technologies (Goodrich, et al., 1995; Li, et al., 1997).

Particle counting is often used to assess removal of bacteria and protozoan cyst sized particles.
Giardia cysts are  approximately  7|im to  14 |im in size, while Cryptosporidium cysts are
approximately 4 |_im to 7 |_im in size. Bacteria can range in size from 0.1 |_im to 100 |im.  Particle
counting  is frequently conducted in discrete size  ranges varying from 2  jam to  100 |_im, and
                                         46

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counts in the 2  |j,m to 15 |j,m range typically used to assess the ability of a process to remove
Giardia and Cryptosporidium.

Table 12 summarizes the results of several MF and UF studies that document the log reduction
of particle  counts  in various  size ranges.  These results show significant reductions in particle
counts for  sizes ranging from 2 |um to 100  |j,m, which encompasses the  size range of many
bacteria and protozoan cysts.  Log removals ranged from 2.9- to 4.7-log for particles in the 3 |j,m
to 5 |im range, which is  similar to Cryptosporidium, and from 1.4- to 4.6-log for particles in the
5 |_im to 15 |_im range, which is comparable to Giardia.  Overall, particle counts were reduced
from 1.4- to 4.7-log over the entire range of 2 |j,m to  100 |j,m.  It should be noted, however, that
these studies have been conducted on natural waters and influent seeding was not performed as it
was in many of the  previously cited studies that used organisms.  Also,  it is  common to have
some detectable level of particles in filtrate, even when the membrane system is integral.  These
factors  result  in  relatively  low  log-removals  compared  to those  observed   in  seeded
microbiological studies.
                                          47

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                    Table 11. MF and UF Studies Documenting Algae Removal Efficiency
Researcher
NSF
NSF
NSF
NSF
Year
2000f
2000c
2000b
2000a
Process
UF
UF
MF
UF
Test Scale
Pilot
Pilot
Pilot
Pilot
Pore Size
0.03 |jm
0.01 |jm
0.1 |jm
1 00,000 MWCO
Water Source
surface water
treated surface water
treated surface water
treated surface water
Log Removal
0.5to>0.9*
>0.6* to >0.9*
>0.6* to >0.9*
>0.7*to 1.2
' indicates removed below detection limit.
                                                   48

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                  Table 12.  MF and UF Studies Documenting Particle Count Removal Efficiency
Researcher
NSF
NSF
NSF
NSF
NSF
NSF
NSF
NSF
NSF
NSF
NSF
Scanlan, et al.
Scanlan, et al.
Kothari, et al.
O'Connell, et al.
Kothari, et al.
Clair, et al.
Year
2000a
2000b
2000b
2000g
2000g
2000e
2000e
2000b
2000d
2000d
2000f
1997
1997
1997
1997
1997
1996
Process
UF
MF
MF
UF
UF
UF
UF
MF
UF
UF
UF
MF
UF
MF
UF
MF
MF
Test
Scale
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pilot
Pore Size
100,OOOMWCO
0.1 |jm
0.1 |jm
150,000-180,000
MWCO
150,000-180,000
MWCO
100, 000 MWCO
100, 000 MWCO
0.1 |jm
0.01 |jm
0.03 |jm
0.03 |jm
0.2 to 0.5 |jm
0.05 |jm
0.2 |jm
100,000 MWCO
0.2 |jm
0.2 |jm
Water Source
treated surface water
treated surface water
treated surface water
treated surface water
treated surface water
surface water
surface water
treated surface water
treated surface water
treated surface water
surface water
surface water
surface water
surface water
groundwater
surface water
surface water
Log Removal
2.2 (total counts)
3.4 to 4.5 (3-5 urn)
3.2 to 4.6 (5 -15 urn)
1 .6 to 4.0 (3 - 5 u m)
1.4 to 3.8 (5 -15 urn)
2.9 to 4.6 (3 - 5 u m)
2.8 to 4.4 (5-15u m)
2.3 (total counts)
1 .5 (total counts)
2.0 (total counts)
3.1 to 4.6 (5-15u m)
2.6 (2 -15 urn)
3.3 (2 -15 urn)
1.9 (2 -100 urn)
Below detection limit for 2
u m
3.6 (2 - 5 u m)
>2.5 (>2 u m)
* indicates removed below detection limit.
+ indicates a broken seal.
++ indicates a potentially contaminated filtrate tank or line.
                                                          49

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3.7    Summary

The  studies cited  in  this section  demonstrate  that membrane processes  are  able to achieve
significant removal of pathogens and other microorganisms.  Integral MF and UF processes can
often reduce protozoan cyst and bacteria concentrations to detection limits.  Since the pore size
of most membranes  is typically  at least an  order of magnitude  smaller  than bacteria and
protozoan cysts, the primary removal mechanism for these organisms is sieving.  UF processes
with pore sizes of approximately 0.01  urn and  smaller can typically achieve virus removal to
detection limits, while MF and UF processes with pore sizes greater than approximately 0.01 |j,m
often exhibit partial virus removal.  However,  virus removal is a impacted by  many  factors,
including the formation of a dynamic cake layer on the membrane surface.  Thus it is difficult to
make generalizations  regarding virus removal  efficiency based solely  on membrane  process
classification.

Although  MF  and UF  membranes are considered absolute barriers for  many pathogens of
concern to the water treatment industry, there are practical and operational  concerns that should
be addressed.  Imperfections in the construction of the membrane module or degradation of the
membrane system  over time can lead to the passage of microorganisms into the treated water.
These imperfections can include broken fibers, scratches in the  membrane  surface, pores larger
than the nominal size, o-rings that do  not seal  properly,  and glue joints that may  be cracked.
Potential integrity breaches such as these  underscore the need for reliable integrity testing,  even
with the superior  microbial  removal performance demonstrated  by numerous  studies.   The
following chapter describes the integrity monitoring techniques commonly used with membrane
processes, including the applicability and limitations of various tests.
                                          50

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4.0   INTEGRITY TESTING
4.1  Overview of Integrity Testing

Integrity testing is a means of assessing whether a membrane system is completely intact or has
been compromised, and it is a critical consideration for any membrane filtration plant. Although
a MF or UF membrane represents a theoretical absolute physical barrier to particles (in the form
of pathogens, turbidity, total suspended solids (TSS), etc.) that are larger than the membrane pore
size, integrity testing represents a practical way of verifying the barrier effectiveness by detecting
leaks or membrane breaches.

There are two general types of integrity test methods:

    1)  Direct Methods: Direct methods are applied specifically  to the membrane or membrane
       module to detect integrity breaches and/or determine their sources.

    2)  Indirect Methods: Indirect methods  are surrogate measures of  integrity that  involve
       monitoring filtrate water quality.  A significant decline in water quality may indicate that
       membrane integrity has been compromised.

Both types of methods may be useful monitoring and/or diagnostic tools for membrane filtration
systems, although there is a trade-off associated with each.  Indirect methods have the advantage
of continuous application while the  system is in operation. However, indirect methods are only
inferential techniques for detecting membrane  integrity problems. The converse  is true for the
direct methods. While the direct methods specifically test the membranes for integrity problems,
current methods cannot be applied continuously and must be conducted while the  system is off-
line.  Direct and  indirect  testing methods  are discussed in detail  in Sections  4.2 and 4.3,
respectively.   Some of the advantages and disadvantages of the various direct and  indirect
methods are summarized in Table 13.

Integrity testing  may be conducted with the  intent of satisfying any  one or more  of several
different objectives.  These objectives include:

    1)  Verification of high quality filtrate water: Because the integrity  of the membrane filter is
       essential  to  achieving filtrate water quality goals, integrity  testing can serve as  an
       indicator of water quality problems. Indirect methods are best suited for this objective, as
       they are designed to monitor water quality.  However, an  integrity breach  detected using
       a direct method of testing would also indicate that the filtrate water quality has  been
       compromised.

    2)  Demonstration of regulatory compliance: As discussed in Chapter 6, direct or indirect
       integrity test methods or a combination of both may be required by  the primacy agency of
       jurisdiction to demonstrate that a membrane filtration system is  successfully achieving its
       allocated  pathogen removal credit and/or other water quality objectives.  Generally, any
       detected compromise in membrane integrity must be promptly addressed, independent of
       the  magnitude  of the breach.   The  implications of membrane  integrity  testing for
       microbial risk and regulation are addressed in Chapter 5.
                                          51

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Table 13.  Summary of Integrity Monitoring Methods
   Integrity Test Method
           Advantages
          Disadvantages
                                                 Direct Methods
Pressure Hold Test
                                  Ability to monitor entire rack of
                                  membranes simultaneously
                                  Ability to detect single fiber breaks and
                                  small holes
                                  Standard part of most membrane
                                  systems and highly automated
                                  Can test both membranes and
                                  downstream plumbing for leaks
                                  Ability to maintain aseptic quality of
                                  system if applied to filtrate side	
                                           Need for increasingly sensitive pressure
                                           transducers when test is applied to
                                           increasingly large number of modules
                                           Potential to yield false-positive results if
                                           the membrane is not fully wetted
                                           Limitation in log removal equivalency
                                           (sensitivity)
Diffusive Air Flow Test
                                  Similar advantages as the pressure hold
                                  test, although typically not included as
                                  standard equipment
                                  More sensitive than the pressure hold
                                  test as currently applied
                                  Ease of conducting and accuracy of test
                                  (when measuring water displacement)
                                           Sensitivity to temperature (viscosity)
                                           Limited full-scale applications to verify
                                           performance
                                           Manual application as currently applied,
                                           though the test can be automated
                                           Not included as standard equipment for
                                           most MF/UF systems	
Bubble Point Test
Ease of conducting and interpreting
results
Ability to identify specific compromised
fibers and leaking seals
Labor intensive for large plants -
manual application
Only able to pinpoint leaks identified by
other test methods
Only practical as a diagnostic test for
the repair of individual modules	
Sonic Sensing Analysis
Identifies compromised module and
general location of integrity breach
Easy to use
Potential to be developed into a
continuous, on-line monitoring method
Manual application
Limited use in the water industry to date
(primarily used as a diagnostic tool at
current state of development)
Labor intensive for large plants
Subjective interpretation of results
Not practical for submersed systems
                                                 Indirect Methods
Particle Counting
Continuous monitoring of filtrate water
quality
Sensitive to minor changes in water
quality
Widespread use and familiarity in water
industry
Difficult to calibrate
Imprecision between different (even
well-calibrated) instruments
Susceptible to sensor clogging
Susceptible to counting bubbles
(entrained air) as particles, or particles
resulting from microbial growth in
instrument tubing
Relatively high cost	
Particle Monitoring
Continuous monitoring of filtrate water
quality
Significantly lower cost than particle
counters
No calibration required
More sensitive to integrity breaches
than turbidimeters but less sensitive
than particle counters
Infrequent use in water industry
Less sensitive than particle counters
Susceptible to sensor clogging
Susceptible to counting bubbles
(entrained air) as particles, or particles
resulting from microbial growth in
instrument tubing
Provides only a relative index of particle
concentration
Turbidity Monitoring
Continuous monitoring of filtrate water
quality
Near comprehensive use at surface
water plants as a result of filtered water
turbidity standards
Significantly lower cost than particle
counters
Relative insensitivity to breaches in
membrane integrity compared to other
methods, although developing laser
turbidimetry may result in comparable
sensitivities
Susceptible to counting bubbles
(entrained air) as particles

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    3)  Detection of equipment / filtration system problems: Integrity testing, by design,  is an
       indicator  of whether  some  components  of a membrane filtration  system  (i.e., the
       membrane, o-rings, seals, etc.) are operating properly.  As a result, independent of water
       quality or regulatory concerns,  an integrity test serves as a diagnostic tool to alert an
       operator to any problem with the system that needs to be corrected.

4.2   Direct Methods

The direct  methods  of integrity testing are  non-destructive  techniques  that  are applied
specifically to the membrane or membrane module in order to identify  and/or isolate leaks.  The
primary disadvantage of direct methods is that they cannot be conducted continuously while the
membrane filtration system is in  operation.  Thus,  the longer and more frequent the integrity
testing, the greater the impact on  system  production capacity.  The frequency of direct method
integrity testing varies with the regulatory requirements of the primacy agency.  Typically, five
to ten  minutes is necessary to conduct a  routine direct integrity  test,  although the system may
remain off-line much longer if a potential integrity breach is detected.

Direct testing methods also indicate nothing specific about  filtrate water  quality.   Thus,  if an
integrity breach is detected, a direct method test will  yield no information on  the impact of that
breach on the filtrate quality.  However, direct methods are not designed to convey water quality
information and are not applied with this objective in mind.

There are  four direct integrity testing methods that are commonly employed to  varying degrees:

    1)  Pressure Hold Test

    2)  Diffusive Air Flow Test

    3)  Sonic Sensing Analysis

    4)  Bubble Point Test

Each of these four types of direct methods is well suited for  particular testing applications.  For
example, the pressure hold and diffusive air flow tests are both first-line integrity tests that are
conducted on racks of membrane  modules. Thus, while these tests are the most expedient and
efficient means to directly test multiple membrane modules, they will  not indicate the specific
module or location within that module where  a  breach has  occurred.  Therefore,  if either the
pressure hold test or the diffusive air flow test detects a problem, follow-up  diagnostic testing
would be  necessary to locate the breach.  For example, a sonic test may be applied to individual
modules within a rack that failed an integrity test  to isolate the module with the integrity breach.
Note that the pressure hold and diffusive air flow tests may require that the membrane rack under
examination be taken  off-line.  Once  the module is isolated and removed from the  rack, the
bubble point test can be used to identify the compromised fiber(s).  The sonic sensing analysis
can be conducted while a rack is on-line, but is not a continuous test.
                                          53

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The four direct testing methods outlined above are addressed in detail in the following sections.
The tests  are discussed as applicable to hollow-fiber membranes.   Spiral wound MF and UF
membranes, although commercially available, are uncommon for  drinking water applications,
and several of the direct methods of membrane integrity testing presented here are not directly
applicable to spiral-wound elements.

4.2.1   Pressure Hold Test

A pressure hold test is conducted by applying pressurized air to the membrane and monitoring
the rate of pressure decay over a specific duration of time.  An outline of the test protocol is as
follows:

   1)  Drain the water from one side of the membrane: Typically, the insides of the fiber lumens
       are drained, which may be the feed or the filtrate  side of the membrane, depending  on
       whether the system is operated in an "inside-out" or "outside-in" configuration.

   2)  Pressurize the drained side of the fully wetted membrane: The applied pressure must  be
       lower than the bubble point of the membrane, which is the pressure required to overcome
       the capillary  forces that hold  water in the membrane pores.  (Bubble point theory is
       further discussed in conjunction with the bubble point test  in Section 4.2.4.)  Pressures
       ranging from  4-30 psi are typically applied during the pressure hold test, depending  on
       the type of proprietary system.  (Membrane construction may limit the pressure at which
       a membrane can be tested.) As further discussed in Section 5.4.1, the applied pressure
       determines the smallest hole that can be  detected by the pressure hold test.  Vacuum
       systems,  which have the feed side of the membrane simply submerged  in basins,  are
       typically tested without  draining the basins.  As a result, the hydrostatic pressure at the
       bottom of the basin must be considered in determining the net applied pressure during a
       pressure hold test performed on a vacuum-driven system.

   3)  Hold the pressure for about ten minutes and monitor the pressure decay: If there are no
       leaks in the membrane, process plumbing, or other pressurized system components, then
       the only way for air to escape is by diffusing through the water contained  in the pores of
       the fully-wetted  membrane.  Estimates of an acceptable pressure decay for an intact
       membrane and leak-free system will vary somewhat by manufacturer.  Typically, higher
       rates of pressure loss are considered acceptable for  composite membranes  since diffusion
       is  significantly greater  through a thin membrane film compared to a homogenous
       membrane of greater thickness.  In general, a pressure greater than 0.1 to  0.5  psi per
       minute may indicate a  leak or breach  in membrane integrity. The specific  threshold of
       acceptable pressure decay rate varies among the different proprietary membrane filtration
       systems and  is a function of both membrane characteristics and the  net  applied test
       pressure.

When applied to a single membrane module,  the  pressure hold test has  been shown to be very
sensitive to leaks  and integrity breaches.  In one test, Adham, et al.  (1995) reported that a
considerable loss of pressure was observed for a  0.6 mm needle puncture in the  lumen wall  of
one out of over 22,000 fibers in a membrane module. Typically, however, the pressure hold test
                                          54

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is  applied to an  entire rack  of membranes  simultaneously  to  test membrane integrity  as
efficiently as possible,  diminishing the sensitivity of the test.   The more membrane modules
included in a single application of the test or the larger the number of fibers (or membrane area
per fiber) per membrane module tested, the greater the number  of pores  through  which the
pressurized air can diffuse.   This, in turn, results in more rapid pressure decay  via diffusion,
diluting the impact of one compromised fiber on the pressure decay rate. As a result,  the greater
the number of fibers tested, the more sensitive the pressure transducers need to be  in order  to
differentiate between normal  diffusive losses spread out over a larger membrane area and losses
due to integrity breaches.

The  dilution  effect that occurs during  the application  of the  pressure hold test to a rack  of
membranes is illustrated through comparison of the results of Adham, et al. (1995)  with those
from  a fiber-cutting study conducted at the Kenosha, Wisconsin microfiltration water treatment
facility.  In summarizing the findings of the  Kenosha study,  Landsness (2001) cites that for a
rack of 90 modules of the same type of membrane tested by Adham, et al., six fibers had to  be
cut before pressure hold test results exhibited any significant variation from the case in which  all
fibers were intact.

Note  that the pressure  hold  test may also be  applied  to  a  single membrane  module to help
pinpoint the source of an integrity problem, although this is seldom done in  practice  in favor of
bubble point testing.

Advantages of the  pressure hold test include:

    1) Ability to measure integrity directly

   2) Ability to monitor an entire rack  of membrane modules simultaneously

   3) Sensitivity  on the order of single  fiber breaks and small holes in the fiber lumen wall
       (The ability of the pressure hold test to detect very small integrity breaches will vary with
       the total number of fibers (and hence total membrane area) to which the test is  applied.)

   4) Standard inclusion in most MF and UF systems

   5) High degree of automation

   6) Widespread use and acceptance by both utilities and primacy agencies

   7) Ability to test both the membrane and downstream plumbing for leaks

   8) Ability to  maintain the aseptic quality  of the system if conducted by  pressurizing the
       filtrate side of the membrane
                                          55

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Some disadvantages are:

    1)  Inability to continuously monitor integrity

    2)  Need for increasingly sensitive pressure  transducers when  the  test is applied to an
       increasing number of membrane modules

    3)  Potential to yield false-positive results if the membrane is not fully wetted
       (This condition  may occur with newly installed and very hydrophobic membranes  that
       are difficult to wet, or when the test is applied immediately after a  backwash process that
       includes air.)

4.2.2  Diffusive Air Flow Test

There are two different  "diffusive air flow tests" described in the literature. Both tests are based
on the same principle as the pressure hold test and  are applied with the same objective of broadly
detecting  leaks in a rack of membrane modules.  The diffusive air  flow tests  differ  from the
pressure hold test in that either air or water flow through the membrane pores is measured rather
than pressure decay.  Both types of diffusive air  flow tests are described as being potentially
more sensitive than the  pressure hold test (Trimboli, et al.  1999). However, these tests have not
been sufficiently developed to gain widespread acceptance by primacy agencies in the  United
States, and applications  of these tests for integrity monitoring in  full-scale  water treatment plants
worldwide are rare at this time.

The most commonly cited diffusive air flow test, discussed by Meltzer (1987), Vickers (1993),
and Cheryan (1998),  involves measuring the diffusion of air through the fully-wetted membrane
pores.  One potential difficulty associated with this test is the  sensitivity of diffusion rates to
temperature.  Seasonal  variations in temperature may cause the results of this test to fluctuate
over the course of the  year, although it is possible  that the results  could be normalized  to  a
standard  reference temperature.  Currently, this test is not in common use in membrane water
treatment plants, and available literature describing the application  of this  test to large-scale
membrane filtration systems is relatively limited.

The other diffusive  air flow test, described in a  1997 report by the American Water  Works
Association Research Foundation (AWWARF) as under development, measures the volume of
water displaced by the pressurized air through compromised fibers. In this report,  Jacangelo, et
al. cite the advantages of this test as its  ease and accuracy of measurement.  Since that report  was
published, a membrane water treatment plant in New Zealand (Joyce  Road Water Processing
Plant, Tauranga, New Zealand) has adopted the use of this integrity test, which  calls for simply
using a graduated cylinder to measure the water flow that would pass  through any compromised
fibers or other integrity breaches in a membrane module (Trimboli, et al.  1999).
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Advantages of the diffusive air flow test include:

    1)  Ability to measure integrity directly

    2)  Ability to monitor an entire rack of membrane modules simultaneously

    3)  Sensitivity on the order of single fiber  breaks and  small holes in the fiber lumen wall
       (The ability of the diffusive air flow test to detect small integrity breaches will vary with
       the total number of fibers (and hence total membrane area) to which the test is applied.
       However, the diffusive air flow test is more sensitive to small breaches than the pressure
       hold test.)

    4)  Ability to test both the membrane and downstream plumbing for leaks

    5)  Ability to maintain the aseptic quality  of the system if conducted by pressurizing the
       filtrate side of the membrane

Some disadvantages are:

    1)  Inability to continuously monitor integrity

    2)  Need  for increasingly sensitive flow monitoring equipment when the test is applied to an
       increasing number of membrane modules

    3)  Potential  to yield false-positive results if the membrane is not fully wetted
       (This  condition may occur with newly  installed and very hydrophobic membranes  that
       are difficult to wet, or when the test is applied immediately after a backwash process that
       includes air.)

    4)  Not included  as part of standard equipment in most MF and UF systems

4.2.3  Sonic Sensing Analysis

A sonic  sensing  analysis is less of an independent testing method than a companion tool to
pressure testing.   If a breach is detected using a pressure hold test, a sonic sensing analysis may
be used to isolate the particular module that contains the  leak.   The analysis is conducted by
manually  applying an accelerometer (an instrument used to detect vibrations)  to one or more
locations  on  each membrane  module.  Using  headphones, the  operator listens for vibrations
generated by  leaking air.

The sonic sensing analysis is most effectively administered by a skilled and experienced operator
and is somewhat more  subjective than  the  other forms of integrity testing,  either direct or
indirect.  Adham, et al. (1995) reported that sonic  sensing was able to detect a breach as small as
a 0.6  mm  needle puncture in the wall of one out of over  22,000  hollow fibers in  one type of
membrane, although  some skill in strategically checking the module was required to identify this
breach.
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Advantages of the manually applied sonic sensing analysis currently in use include:

    1)  Ability to measure integrity directly

    2)  Identification of compromised module and general location of breach

    3)  Ease of use (assuming the test is conducted by a trained operator)

    4)  Potential to be developed into a method of on-line, continuous, direct testing

Some disadvantages are:

    1)  Inability to continuously monitor integrity

    2)  Manual application

    3)  Limited use in the water industry to date

    4)  Potential to be labor intensive for large plants

    5)  Potential for subjective interpretations of results

    6)  Not practical immersed membrane systems

An automated and computerized sonic testing system could have the  potential to eliminate the
subjectivity of this test and serve as an on-line, continuous, and direct means of integrity testing.
The early-stage development and testing of such an automated sonic system was described in a
paper by Glucina, et al. (1999).  This new acoustic monitoring system utilizes a sensor on each
membrane module to detect changes in noise caused by pressure fluctuations in a compromised
fiber.  Test results indicated that the automated acoustic system was capable of detecting a single
compromised fiber, although performance  was affected by the level of background mechanical
noise  associated with the membrane filtration system.  In addition, greater noise was  generated
by higher flows through a compromised fiber, rendering the breach  easier to detect relative to the
background noise. The system described by Glucina, et al. (1999) remains under development
by the manufacturer.

4.2.4   Bubble Point Testing

Bubble point testing,  like sonic testing,  is best employed  in conjunction  with the pressure hold
test rather than as a separate and independent gauge of membrane integrity.  For example, after a
pressure hold test is used to detect an integrity problem and a sonic sensing analysis isolates the
module containing the leak, the bubble point test can be applied to a  identify the compromised
fiber(s) following its  removal from the rack.

The bubble point test is based on capillary theory, in which the "bubble point" is defined as the
gas pressure  required to displace  liquid from the pores  of  fully-wetted filtration  media.   In
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conducting a bubble point test, the module to be tested is first removed from the rack.   The
external shell of the module is then drained and pressurized to a pressure below the bubble point
of the membrane.  Applied pressures are generally similar for the bubble point and pressure hold
tests for the same  type of proprietary membrane.  A dilute surfactant solution is applied to the
open ends of the membrane fibers at the end  of the module.  The formation of bubbles in the
surfactant solution  can be used pinpoint specific leaking fibers.

Advantages of the bubble point test include:

    1)  Ability to measure integrity directly

    2)  Ease of conducting and interpreting results

    3)  Ability to identify specific compromised fibers and leaking seals so as to facilitate repair

Some disadvantages are:

    1)  Inability to continuously monitor integrity

    2)  Manual application

    3)  Requires removal of a membrane module from the rack

    4)  Potentially  labor intensive for large pressure-driven (i.e., encased) membrane systems

    5)  Only a useful tool for pinpointing leaks that have already been identified by other testing
       methods when applied to pressure-driven (i.e., encased) membrane systems

4.3  Indirect Methods

Indirect methods of integrity  testing  do not apply  specifically to the membrane or module, but
rather monitor some component of  filtrate  water  quality  as  a surrogate measure of integrity.
Because the membrane filtrate water quality is typically very consistent and is independent of the
feed water quality,  a marked decline in filtrate quality may indicate an integrity problem.

While  the indirect methods  have the  disadvantage of only  being  able to  suggest potential
integrity  problems, there are some benefits to using these methods.   First, the most common
methods of indirect testing operate in a continuous, on-line mode. In addition,  the same  indirect
methods  and testing  instruments  can be  applied to  any membrane system, independent  of
manufacturer,  system configuration,  or any other parameter  intrinsic to a proprietary  system.
Moreover,  indirect methods  are likely  to remain  applicable to any new systems that are
developed. It should be noted that systems that use air for backwash, or to control fouling in the
case of some submerged systems, are more  susceptible to interference by entrained air bubbles,
which may make development of a stable baseline more difficult.
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The three indirect testing methods  that are employed in the majority of membrane  filtration
applications are as follows:

    1)  Particle Counting

    2)  Particle Monitoring

    3)  Turbidity Measurements

The above  methods are listed  in  order of  decreasing  sensitivity  to  integrity breaches  as
determined in a study of integrity test methods conducted by Adham, et al. (1995).  Each of these
methods, as well as several less common indirect techniques for detecting integrity problems, are
discussed as follows  in Sections 4.3.1 - 4.3.4.

4.3.1  Particle Counting

Particle counters use a  laser-based light scattering technique to count particles and group them
according to size. Although Adham  et al. (1995) determined that particle counting was  the most
sensitive of the three common on-line indirect methods,  particle  counting instruments have a
number of well-established operational problems  that can potentially distort both the  accuracy
and precision of their measurements.

Advantages of particle counting are as  follows:

    1)  Sensitivity to relatively  minor water quality changes that may result from a breach

    2)  Widespread use  and familiarity in the water treatment industry

    3)  Continuous monitoring  of filtrate quality

Some disadvantages  are:

    1)  Difficulty to calibrate in the field

    2)  Imprecision between different instruments
       (Two identical, well-calibrated  devices may yield significantly different readings for the
       same water source.)

    3)  Susceptibility to "coincidence error"
       (Two or more particles  may pass through the sensor simultaneously, causing the count to
       be underestimated.)

    4)  Susceptibility to sensor  clogging or obscuring, particularly in turbid waters

    5)  Susceptibility to counting bubbles as particles as a result of air entrainment
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    6)  Susceptibility to counting particles shed from connective piping or tubing on the filtrate
       side of the membrane (i.e., from microbial growth, corrosion, etc.)

    7)  Unrepresentative (unstable) output during startup and shutdown

    8)  Cost of particle counters relative to other integrity monitoring instrumentation

These disadvantages have significant implications for the use of particle counters as a means of
integrity monitoring. First, because particle counting is not an absolute measure of water quality,
relative changes in particle concentration must be used to determine whether a breach of integrity
has occurred.  A baseline and relative deviations that would signal a potential breach would have
to be established  for  each individual particle counter.   If a particle  counter  is  sufficiently
sensitive, then small breaches would be easily detectable relative to baseline measurements. The
factors affecting instrument sensitivity are discussed in Chapter 5.

Due to variability in particle counters, a specific instrument could only be used for the particular
membrane rack filtrate to which it is attuned and for which the relative deviation of concern is
known.  Switching particle counters (or sensors) or recalibrating the instruments would  require
re-attenuation for each of the affected  instruments to the particular filtrate waters to which they
are applied.   However, it would  be feasible  to multiplex a number  of sensors to an individual
particle count instrument if the individual sensors are attenuated to a specific rack.

The susceptibility of particle counters to coincidence error and sensor clogging may not present a
significant problem for these instruments  when applied to monitor  membrane filtrate.  The
potential for both of these errors is  heavily influenced by water quality.  The higher the particle
concentration and/or  turbidity  of  the  water,  the  more subject  these  instruments  are  to
underestimating the particle counts.   However, since MF and UF membrane filtrate typically has
a very low particle concentration and turbidity, even under compromised conditions, coincidence
or clogging errors are not likely to occur.

The potential for  air  entrainment  to  cause  particle counters  to report overestimated  results
presents a more substantial problem. Significant air may be introduced into the piping during the
periodic membrane backwashing, particularly if air is used to scour or  pulse the membrane
during the backwash cycle. As a result, after  backwashing, the effective use of particle counters
as an integrity monitoring tool  is somewhat diminished until the air  is expelled and the particle
counts return to baseline levels.  The time required for this air purge varies with the particular
membrane system and the backwash operating parameters.  The  implications of this error for
integrity testing and microbial risk are discussed in Section 5.4.2.

The cost of particle counters can vary depending on the sensitivity of the instrument, i.e., the
more sensitive an instrument is to small particle size ranges, the more expensive it is likely to be.
The higher cost of particle counters (relative to other instruments used for indirect monitoring)
also has implications for integrity testing.  Generally, the more expensive an instrument is, the
greater the motivation to develop  a monitoring scheme that minimizes the number of instruments
required.  However, the fewer the number  of particle  counters in  operation,  the  greater the
number of membranes  modules that will be monitored by each device.  As a result, the impact of
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an integrity breach  is  diluted,  and the ability of a  particle  counter to detect  the  breach is
diminished. The cost of implementing particle counting as means of integrity monitoring may be
moderated somewhat by the use of a multiplexing system to  connect sensors  on a number of
different membrane racks to  a single  instrument, however,  this would prevent continuous
monitoring of every rack.  A similar cost-saving technique could also be applied  in using particle
monitors and turbidimeters, as well.

4.3.2  Particle Monitoring

Particle monitors  operate  on the principle  of light obstruction,  similar to particle counters.
However, rather than counting particles and grouping them by size, particle monitors measure
paniculate water quality on a dimensionless scale relative to an established baseline.

Particle monitors are significantly less expensive than particle counters and were  determined to
be more sensitive to integrity breaches than turbidimeters (Adham,  et al.,  1995).   However,
particle monitors are seldom used by utilities, and thus the water industry has limited experience
with these devices.  Moreover, particle monitors are subject to some of the same  disadvantages
as particle counters.  The advantages and disadvantages of particle monitors  are summarized
below:

Advantages of particle monitors include:

    1)  Lower cost than particle counters

   2)  Greater sensitivity to integrity breaches than conventional turbidimeters

   3)  Continuous monitoring of filtrate quality

Some disadvantages  of particle monitors are:

    1)  Infrequent use in the water industry

   2)  Lower sensitivity to integrity breaches than particle counters

   3)  Susceptibility to "coincidence error"

   4)  Susceptibility to sensor clogging or obscuring, particularly in turbid waters

   5)  Susceptibility to counting of bubbles as particles as a result of air entrainment

   6)  Provides only a relative index of particle concentration
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4.3.3  Turbidity Measurements

Conventional turbidimeters  measure light  scatter  due to the  presence  of particulate matter in
water.  These instruments have been shown by Adham, et al. (1995) to be less sensitive than both
particle counters and particle  monitors for detecting integrity breaches; however,  a newly
developed  laser  turbidimeter  may hold  more  promise  for  indirect  integrity  monitoring.
Manufacturer  specifications indicate that  the  laser turbidimeter  has increased sensitivity in
excess of two orders of magnitude over conventional turbidimeters and is optimized to measure
very low turbidities, in the range of 0 - 1 NTU.  These abilities have been documented in a study
conducted by Banerjee, et al. (1999a).  Since most MF  and UF systems produce filtrate water
consistently in  the range of 0.01 - 0.05 NTU, the  laser turbidimeter  may be well suited to
monitor membrane filtrate.

In another  study conducted  by  Banerjee, et  al. (1999b) with different collaborators, the laser
turbidimeter and one  type of particle counter (from the same  manufacturer) tracked changes in
water quality caused  by particles larger than  2 u,m  with  similar success, although the data
collected by the laser turbidimeter appeared  to exhibit greater resolution.   In addition,  a third
study conducted by Banerjee et  al. (2000), with  still a different set of collaborators, demonstrated
that the ability  of the  laser turbidimeter to detect changes in water quality caused by cutting a
single membrane fiber in a test  module was on  par with that of a particle counter. The results of
at least one recent study, however, indicate that the laser turbidimeter is  somewhat less sensitive
to integrity breaches than  particle  counters  (Colvin,  et  al., 2001).    Thus, although  the
effectiveness of the relatively new laser turbidimeter  as an indirect method  of integrity testing is
still being  evaluated by the  water industry, research conducted to date generally indicates that
these devices are more sensitive to integrity problems then conventional  turbidimeters and seem
to be comparable to particle  counters.

Like particle counters, continuous, on-line  turbidimeters  may also be  subject to  air entrainment
error. Typically, bubble traps are  employed with turbidimeters (both  conventional and laser) to
minimize or eliminate this error. However, neither conventional nor laser turbidimeters share the
same accuracy  and  precision difficulties that are problematic  for particle counters.  Two well-
calibrated turbidimeters are likely  to yield similar  results  for the same water.  Conventional
turbidimeters, which are employed  in vastly greater numbers in water treatment plants than the
relatively new laser  turbidimeter, are also significantly less expensive than particle counters.  In
addition, turbidimeters have the added advantage of measuring a parameter that is both absolute
(as  opposed  to a relative measure, as with particle monitors) and widely recognized as  a
meaningful gauge of water quality from  a regulatory perspective.

Advantages of conventional  turbidimeters are summarized as follow:

    1)  Near comprehensive use at surface water  treatment plants throughout the  country  as a
       result of surface water treatment regulations

   2)  Lower cost then particle counters or particle monitors
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    3)  Consistency of measurement
       (Two well-calibrated turbidimeters will yield similar results for the same water.)

    4)  Ability to measure water quality with respect to paniculate  matter in absolute terms  (as
       opposed to particle counters)

    5)  Continuous monitoring of filtrate quality

Some disadvantages are:

    1)  Relative insensitivity to breaches in membrane integrity compared to other indirect
       methods

    2)  Susceptibility to air entrainment error

The advantages and disadvantages associated with laser turbidimeters are  similar to those listed
for conventional  turbidimeters.   However, the  sensitivity  of laser  turbidimeters to changes in
filtrate water quality is significantly greater than that of conventional turbidimeters.

4.3.4  Other Indirect Methods

Other indirect methods of integrity testing include seeding studies, silt density index (SDI) tests,
and batch particle count tests.   These tests cannot be conducted  continuously or on-line,  are
logistically more  difficult to implement than the on-line methods, and require substantially more
time to complete. Thus, these tests lack the primary advantages of both the direct and indirect
tests.   As a result, these tests are not considered practical  for integrity monitoring at full-scale
water treatment plants.

One recently developed method of indirect integrity testing is a variant of particle counting that
involves periodically spiking the membrane feed water with powdered activated carbon (PAC)
(van Hoof,  et  al.,  2001).  Because the addition of the chemically inert  PAC increases the
concentration of particles in the feed water, the  resulting filtrate will also be higher  in particle
counts under conditions of compromised  integrity.  This  increase in particulate concentration
facilitates  detection of an  integrity  breach   by  particle counters, particle monitors,  or
turbidimeters.  (The effect of feed water quality  and other  parameters on the sensitivity of
integrity testing methods is further discussion in Chapter  5.)  Like other common methods of
indirect integrity  testing, particle spiking is an on-line  test  but not continuous.  In addition, the
more frequently a particle spiking test is conducted, the greater the  usage  and associated cost of
the spiking  agent.   The particular particle spiking method utilizing PAC as described  by van
Hoff, et al. (2001) was  applied to a UF water treatment plant in Europe. This page  intentionally
left blank.
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5.0   MEMBRANE INTEGRITY AND MICROBIAL RISK	

5.1   Driving Force for Integrity Testing

Microfiltration and ultrafiltration membranes have been demonstrated to be effective barriers to
particles and microorganisms that  are  larger than the membrane exclusion  characteristic,  as
discussed in Chapter 3.  In addition, it has been shown that even with an integrity breach that is
sufficiently small, membrane filtration  systems have the ability to achieve pathogen removal
above that  normally  possible  with conventional  treatment processes.    For  example,  an
AWWARF study (Jacangelo,  et al., 1997) demonstrated that with one of 22,400 fibers cut, a
specific MF membrane  was still able to achieve 3.9-log Giardia and 4.6-log  Cryptosporidium
removal.  However, primacy  agencies  in general have chosen not to link various  degrees of
integrity loss with  incremental reductions in log removal  credit.   Instead, primacy  agencies
typically require any identifiable integrity breach to be promptly addressed, independent of the
magnitude of the breach  or its particular implications for risk of microbial passage.  While a
utility may have confidence that its membrane filtration system has an implicit factor  of safety
for the protection of public health even  with a small degree of integrity loss, it is still obligated
take steps to correct the problem  immediately.   One exception  to this general approach to
membrane regulation has been developed in the state of Wisconsin, which  requires  membrane
filtration plants to correlate degree of integrity loss with reduction in log removal capability. The
state then uses this data to establish facility-specific action levels for integrity loss based  on the
results of regular integrity monitoring.  An  overview of nationwide state  regulatory policies is
presented in Chapter 6.

Both  direct and indirect test methods are used to monitor membrane integrity and detect defects
or breaches that could allow feed water to bypass membrane filtration.  Most new  membrane
filtration systems are factory-equipped with the  ability to automatically  conduct this  test at
operator-defined intervals.  In some  cases,  primacy agencies require utilities  with  membrane
filtration systems to  conduct a pressure hold test as frequently as  every four hours,  an interval
that corresponds  with the turbidity  monitoring frequency for conventional media  filters.   In
addition, commonly  employed indirect  methods,  such  as  particle counting  and  turbidity
measurements,  are  applied on-line to  continuously monitor for  water quality  changes as  a
surrogate measure of membrane integrity.  These indirect methods can also detect  small integrity
breaches under certain conditions.  Thus, the tools are readily available to identify compromises
in the membrane filtration system with a frequency as often as a pressure hold test is  conducted,
and potentially  almost instantaneously depending  on the sensitivity of the on-line indirect test
methods that are utilized and the magnitude of the breach.

With  an obligation to repair any compromise in membrane integrity promptly and the means to
quickly detect breaches readily available, the primary driving force for membrane  integrity
testing has been less related to the microbial risk associated with various levels of integrity loss
than on the potential for any microbial risk at all.  As a result, the regulatory community has in
general directed  its  efforts toward  the minimization of microbial  risk  by  focusing on  the
immediate detection and elimination of any breach in membrane integrity.
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Therefore,  the  optimization (i.e., maximizing the efficiency and  effectiveness) of membrane
integrity testing, in terms of the applicability of the various tests, ease of testing, minimization of
off-line time, test sensitivity, etc., is of primary importance.  This  section addresses the factors
that affect  the optimization of membrane integrity testing,  as well as the implications of these
factors with respect to the water treatment industry's confidence in the ability  of membranes to
reliably remove pathogens.

5.2   Integrity Breaches

Most  membrane integrity problems result from factory defects (e.g., in  the processes of fiber
spinning, potting, or sealing) or damage incurred during shipping.  These integrity problems may
become manifest during normal operation, system pressurization, or backwashing and  are likely
to be  detected shortly after the installation of the membranes.  Integrity  problems may also be
caused by  improper maintenance (e.g., failing to properly  seal the module, improper chemical
cleaning, or careless handling of the membrane) or structural creep of the fibers over the life of
the membrane.   Chemical degradation may create  integrity problems as well, which may result
from filtering water outside the recommended pH range, cleaning the membranes with solutions
outside the recommended  pH  range,  or the accidental  exposure  of  an  oxidant-intolerant
membrane  to a pre-oxidant or disinfectant used upstream in the treatment process.

Integrity breaches may occur in any of several locations in the membrane module, including the
seals,  the membrane potting, or in the fibers.  In general, there  are two  types of compromised
fibers: broken or punctured.  Broken fibers are completely compromised  across the entire fiber
diameter, while punctured fibers have holes in the fiber wall.

Once  compromised  fibers have  been  identified  using  integrity  test methods,  they can  be
individually isolated and taken out of service by inserting specially designed pins  or epoxy into
one or both ends, depending on whether filtrate  is withdrawn or  feed is fed from both ends.
These  pins effectively seal off the  damaged fiber. Addressing seal leaks may be a  matter of
replacing the o-rings, while cracks in the potting or other problems, such  as structural  defects in
the module headpieces which connect a module  to the rack,  may  require factory service or
module replacement.

5.3   Factors Affecting Direct Methods

5.3.1   Pressure-Driven Methods

All three of the pressure-driven methods  for direct integrity testing - the  pressure hold test, the
diffusive air flow test, and the bubble point test - are governed by  capillary theory as  described
by the bubble  point equation.   The bubble point is defined as the gas pressure required to
displace liquid from the pores of a fully wetted membrane. The bubble point equation is derived
from a balance of static forces on the liquid meniscus in a capillary tube, and is  expressed as
follows:
                   D    )
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       where:  P = bubble point pressure
               k = pore shape factor
               G = surface tension of the capillary liquid
               9 = liquid-capillary tube contact angle (or the "wetting angle")
               D = capillary (or pore) diameter

The bubble point test was originally developed to characterize pore sizes in membranes.  When
bubbles are first detected at a certain threshold pressure, the bubble point equation can be used to
calculate the diameter of the largest pore.   As  a conservative example, by  assuming a water
temperature of 20°C (implying a surface tension of 73  dynes/cm), a shape factor of  1 (i.e.,  a
perfectly cylindrical hole), and a wetting angle of 0°, rearranging the variables, and applying the
proper conversion factors to yield convenient units,  the bubble point equation  may be simplified
as follows (Cheryan, 1998):

                    41.6
        D(fjm) =
                  P(psig)

Note that the pressure required to displace air from the capillary tube is inversely proportional to
the size of the pore.  Therefore, the smaller the pore size, the greater the required pressure to
force air through the pore.  Applying this equation to integrity testing,  the smallest size hole in a
fiber that can be detected is limited by the maximum rated   transmembrane  pressure of the
membrane. Conservatively assuming that a commercially available membrane would be able to
withstand a maximum test pressure of 100 psi (although this will vary  from product to product),
the smallest size hole that would be able to be detected using the pressure hold or bubble point
tests is just over 0.4  u,m.  A hole this size is near the low threshold of bacteria sizes (~ 0.7 u,m)
and about an  order of magnitude smaller than the smallest protozoan cyst (~ 3 u,m).

A typical test pressure range specified by membrane manufacturers for conducting pressure hold
tests is approximately 15-20 psi, which translates into minimum detectable hole sizes  of about
2-3 |j,m.  Although the membrane may be  completely intact and contain no holes smaller than
this range, a pressure-driven test  conducted in this range would not be  able to demonstrate
integrity on a finer scale.  While holes smaller than 2-3 u,m would allow the passage of virus
and some bacteria through the membrane,  demonstrating  integrity  to  this size  pore should
indicate the removal of Giardia (-6-20 u,m) and Cryptosporidium (-3-8 u,m).

Demonstrating  integrity to the  degree necessary to remove viruses  is  more  problematic.
Extending this conservative example,  in order to physically demonstrate  that a membrane is
intact to a  degree such that even the largest size virus (~ 0.1  u,m)  is completely removed, a
pressure hold test would have to be conducted at over 400 psi, well-above the pressure rating  for
any MF and UF membrane in use for water treatment.

Applying the bubble point equation with parameters that may be more  typical of commonly used
membranes (k = 0.25 and  9 =  45°), only about 75 psi would be necessary to detect a breach
comparable in  size  to the largest virus using the pressure hold  test;  however, a prohibitive
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~ 750 psi would be required to detect a breach on the order of the smallest virus (~ 0.01  um).
Conversely, at typical test pressures of 15 - 20 psi, the  smallest breach that can be detected is
about 0.4 - 0.5  urn, a range well exceeding the size of even the largest virus particles.  Thus, at
these applied pressures, a successful pressure hold test would provide no indication of whether
smaller breaches,  still  capable of allowing  significant virus passage, were present in the
membrane module.

The  limitations of the pressure-driven integrity test have significant regulatory implications.  If
the ability to demonstrate continued removal capability on a regular basis via integrity testing is
the criterion by which  primacy agencies judge whether to  grant pathogen removal  credit
commensurate with the performance specifications of the system, then significant virus removal
credit is difficult to justify.  Thus, even though  challenge studies have demonstrated that UF
membranes are capable of removing viruses, without the means to continually, consistently, and
practically verify this removal over the course of system operation, primacy  agencies may be
unwilling  to grant virus  removal credit.   Cheryan   (1998)  noted this  issue  in  his  text,
Ultrafiltration and Microfiltration Handbook,  indicating that the  lack of an integrity  validation
test largely prevents UF membranes from being accepted as "sterilizing filters."

However, the bubble point equation can be used to illustrate why the pressure hold test can be
effective for  detecting integrity breaches as small as a single cut fiber.   Applying the equation
with conservative parameters (k = 1  and 9 = 0°) to a membrane fiber with a  diameter as small  as
100 um demonstrates that a pressure of only 0.4 psi is necessary to demonstrate integrity on the
order of a single cut fiber. Thus, at typical test pressures of 15 - 20 psi, a single cut fiber would
readily produce a response. However, the inability of integrity testing  to detect  a hole on the
order of 0.1  urn may be a significant factor  in the reluctance  of state  agencies to grant  virus
removal credit to UF membranes.

The  vacuum  hold test is variation of the pressure  hold test in which a vacuum is  applied to the
drained side  of a fully wetted membrane and  the vacuum pressure decay rate monitored.  The
vacuum hold test is limited to test pressure of -1 atmosphere (-14.7 psi), which corresponds to a
minimum  detectable breach size of approximately 0.5  um applying the bubble point equation
and typical operating parameters (k = 0.25 and 6 = 45°). At this applied vacuum  pressure, the
vacuum hold test could detect  leaks smaller than Giardia,  Cryptosporidium, and most bacteria,
but would not be able to verify integrity in the size range of virus particles.

Another factor  limiting the maximum test pressure or vacuum  at which  a pressure- or vacuum-
driven test can be applied is the trans-wall symmetry of the membrane fiber (see Section 2.2.1).
For composite  membranes, the rate of diffusion through liquid filled pores can be significant,
resulting in increased pressure loss during a pressure-driven test  that would still be considered
indicative  of an integral membrane.  Homogeneous membranes face a different concern during
pressure hold testing.  When air is applied to the permeate side  it can become trapped in the
small pores near the dense outer layer of the membrane and may  not be displaced when normal
operation is resumed.  This effectively reduces the thickness of the dense outer layer, resulting in
increased strain on the fiber, potentially resulting  in fiber damage. This is  less of a concern in
composite membranes where the air-water interface is maintained  at the  outer thin film resulting
in less air binding in the membrane pores (Cote, 2001).

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5.3.2  Sonic Methods

As a manually applied test, one significant limitation of the sonic sensing analysis is the potential
subjectivity of the test when employed to identify very small leaks (i.e., on the order of a pin-
sized hole  in the fiber wall, or smaller) that may be difficult for an operator to identify.  The
ability of the test to detect such membrane integrity problems may be dependent the operator's
skill in interpreting the sounds transmitted by the sensor.

At its current state  of development,  the sonic sensing analysis is not employed as a primary
means of detecting leaks, but rather  as  a diagnostic tool for helping to isolate a leak that has
already been detected.  As a result,  optimization of current sonic sensing technology as an
integrity monitoring tool does not have significant implications for the minimization of microbial
risk.

However, sonic testing techniques may have the  potential to be developed  into an integrity test
method that is direct,  on-line,  and  continuous.   An automated sonic test  could  continually
monitor  sound waves  emanating from the membrane  module and compare them to a baseline
established on a module that is  known to be  integral.  If the results were  to vary significantly
from  preset baseline parameters, an alarm could provide instant notification.  This test  would
eliminate any subjectivity of current sonic sensing analysis, and, if sufficiently sensitive to very
small leaks uniformly throughout the  membrane module, it could be used as a first line integrity
monitoring tool.  The development of such an on-line,  continuous sonic integrity testing method
is described by Glucina, et al. (1999) and is summarized in Section 4.2.3.

5.4   Factors Affecting Indirect Methods

5.4.1   Common Factors Affecting Indirect  Method Sensitivity

Although particle  counters,  particle monitors, and turbidimeters do  not directly test membrane
integrity, they are on-line methods which continuously monitor filtrate quality.  These methods,
if sufficiently sensitive,  can be  an effective  integrity monitoring tool and complement direct
integrity testing.

Since each of these methods provides an indication of integrity  through excursions  in  filtrate
water quality relative to a baseline value, the sensitivity of each method depends on the impact of
the breach on filtrate water  quality.  Water from  a breach will have elevated levels of particles
and turbidity; however, these high concentrations will be  diluted by the filtrate,  potentially to
levels that would be indiscernible to indirect monitoring instrumentation.  The  amount of dilution
that occurs is a direct function of the  flow and particle concentration from the breach relative to
the flow and particle  concentration from all  intact fibers.   The  greater the flow and particle
concentration from  a  breach, i.e., the greater the severity  of  the breach, the more likely an
indirect method will be capable of detecting the breach.  This link between  filtrate water quality
and method sensitivity also  implies a link between sensitivity and microbial risk, in that  higher
particle concentrations and/or turbidity imply higher pathogen concentrations.

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The following factors impact the flow or particle concentration from a breach, relative to intact
fibers, and thus the sensitivity indirect integrity methods:

   1)  Feed Water Quality: A higher concentration of particles (i.e., pathogens, TSS, turbidity,
       etc.) in the membrane feed water will result in a greater concentration of particles from an
       integrity  breach.  Thus,  indirect integrity monitoring instruments are  more sensitive to
       integrity breaches at higher feed water particle concentrations.

   2)  Mode of Operation: Although mode of operation has  been used primarily to indicate
       whether a membrane filtration system is  configured in a dead-end or cross flow pattern,
       the diversification  of proprietary  system  types  and configurations necessitates  that  a
       broader definition be used.   Thus,  for the purposes of this analysis, the two modes of
       interest are differentiated as: a) those systems that concentrate paniculate matter in the
       bulk feed solution;  or b) those systems that do not concentrate particulate matter in the
       bulk feed solution  to an appreciable  extent.   Two types of systems that concentrate
       particles in the bulk feed solution are cross-flow systems and vacuum systems operated in
       the direct mode with feed and bleed.

       The effect of operating mode on instrument sensitivity is illustrated by the example of
       cross flow operation, in which the concentration  of particles/turbidity  in the bulk feed
       solution  continuously  increases over the course of a  filtration  cycle (i.e., between
       backwashes).  The  1997 AWWARF study  conducted by  Jacangelo, et  al.  demonstrated
       that this artifact of operating in a cross flow mode  could impact the sensitivity of indirect
       integrity monitoring methods.  In this study, the sensitivity of particle counters to a single
       fiber break was consistently  found  to increase over the course of a filtration cycle.  A
       similar effect was  not  observed for the dead-end flow  mode of operation,  in which
       particulate matter in the bulk feed solution  is not concentrated to an appreciable extent.
       Thus, the mode of operation can affect the particle concentration from a breach, which in
       turn affects the sensitivity of the instruments used for indirect integrity monitoring.

   3)  Location of Fiber Break: For systems that concentrate particulate matter in the bulk feed
       solution,  the particle concentration gradients will increase from the process influent to the
       process  effluent.   As a  result, a break near the  process  effluent will  result  in greater
       contamination of the filtrate relative to a break near the influent.  Consequently, indirect
       methods are more sensitive to integrity breaches near the process effluent.

   4)  Number of Fibers per Module: The greater the number of fibers in a given membrane
       module, the smaller the flow contribution and resulting  impact on filtrate quality from a
       single broken fiber. Consequently, indirect methods are more sensitive to fiber breaks in
       modules with a smaller number of fibers.

   5)  Fiber Diameter:  The smaller the diameter of a broken membrane fiber, the smaller the
       flow contribution and  resulting impact  on filtrate quality from  a single  broken  fiber.
       Thus, indirect methods are less sensitive  to fiber breaks in modules with small diameter
       fibers.
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    6)  Transmembrane Pressure: As the TMP is increased, the permeation of water through the
       pores of intact fibers increases, as does the flow from integrity breaches.  However, in the
       majority of cases, an increase in TMP will  result in  a greater relative increase in the
       filtrate flow from intact  fibers.  This will  lead to further dilution of particles  from the
       breach, resulting in decreasing indirect method sensitivity with increasing TMP.

    7)  Membrane Fouling: As the membrane fouls,  resistance to water permeation through the
       pores of intact fibers increases,  and the  TMP  is  typically increased to  maintain
       production.   This will result in increased flow through broken fibers relative to flow
       through intact fibers, assuming that  foulants are not large enough to plug broken fibers.
       The  increased flow through broken fibers will have a greater impact  on filtrate water
       quality.  As a result, indirect methods become more sensitive to integrity breaches as the
       membrane fouls.

For each application of an indirect integrity monitoring technique, there is a minimum change in
water quality resulting from an integrity breach that can be reliably detected.  Using a theoretical
calculation as applied to two types of proprietary  membranes, researchers conducting  the  1997
AWWARF  study tried to determine the smallest breach, or threshold, that could be  detected by
three indirect monitoring instruments.  The  threshold is expressed in terms of the largest number
of fibers that can be monitored using an indirect monitoring technique while still being capable
of detecting a single fiber break. For both turbidimeters and particle monitors, the threshold was
smaller than the number of fibers contained in  a  single module of one type  of  membrane,
indicating that  these  devices were ineffective for detecting a single fiber break. For particle
counters, on the other hand, it was shown  that for this type of membrane one instrument could
monitor 29 modules and still detect a single cut fiber.  However, for another type of membrane
with an order of magnitude more fibers per module, a particle counter would only be  able to
detect a single cut fiber over two modules.  This apparent discrepancy was attributed to the mode
of operation.  The module with the most fibers  was operated in  a  dead-end mode (i.e., no
significant concentration of particles on the feed side), where as the module with fewer fibers
was operated in a cross-flow mode (i.e., significant increase in the concentration of  particles on
the feed  side over a filtration  cycle).  Thus, if it is necessary  to detect a single cut fiber over a
membrane rack to minimize  microbial risk, particle counters may  not  be an economically
feasible  means  of integrity testing for at  least some  types  of membranes.   Furthermore,
turbidimeters and particle  monitors,  which are  less  sensitive instruments, may be  neither a
technically nor an economically feasible means of monitoring to this level of integrity.

Although indirect monitoring  techniques have sensitivity  limitations, there is still utility in the
application  of these techniques to membrane filtration  systems.   Due  to the  current lack of
continuous,  direct  methods of  integrity testing  for widespread  application  at MF  and UF
facilities,  indirect methods  are  the only available means for monitoring system performance
between  periodic applications  of more sensitive direct testing  methods. Thus, indirect methods
may complement direct integrity testing even if they cannot detect  single fiber breaks in  most
full-scale water treatment plant applications.  Also, it is important to note that the dilution effect
that makes it difficult to detect small breaches using  indirect methods also reduces the impact of
these small breaches on filtrate quality and microbial  risk.
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Some  specific issues  associated  with particle counters and turbidimeters  are  addressed in
Sections 5.4.2 and 5.4.3, respectively.

5.4.2  Particle Counters

One factor endemic to particle counters that hinders the ability of these devices to detect integrity
breaches is their susceptibility to false positive readings from bubbles resulting from air that may
be  entrained during some backwash  procedures.  The particle count spikes that  occur after
backwashing may confound the ability of an  operator to distinguish backwashing effects from a
fiber break for a period of time  after the backwash cycle,  particularly if other factors have
minimized the sensitivity of the particle counters.  This potential inability to detect leaks may
increase the microbial risk from a regulatory perspective.

However, a prudent monitoring protocol may allow an operator to distinguish fiber breaks from
air  entrainment error.   First,  it may be possible to  define the periodic particle  count profile
associated with the backwash cycle and effectively  use that profile as a baseline.  Adham, et al.
(1995) observed  that the  phantom particles detected following a  backwash  cycle  generally
ranged from 0.5 - 1.0 |j,m, whereas particle counts  in the size range  of 1.0 - 2.0 um were most
affected by cutting one fiber in a simulated  integrity breach.  The success of this technique is
dependent  on the ability of a skilled operator to distinguish the normal backwash profile from
aberrations that may occur and is dependent on the magnitude of the backwash profile relative to
elevated particle counts caused by  an integrity breach.  Alternatively,  depending on the degree of
system automation, the  software controlling the particle counters may be programmed to  ignore
the data spikes attributable to air entrainment  during backwashing.

The variety of potential problems associated with  particle  counters, including air entrainment
error, coincidence error, particle shedding error, clogging, instrument variability, and calibration
difficulties (as discussed in Section 4.3.1),  as  well  as  questions about the sensitivity  of the
instruments, cast  significant uncertainty on the utility, reliability, and practicality of using these
devices as a sole means of membrane integrity monitoring.  Furthermore, the applicability of
particle counters  for systems that use air for backwashing or to prevent fouling  is a  concern.
Moreover,  there   is  some  doubt  regarding  the  usefulness of particle  counters  in general
throughout the water industry.  However, the  requirement of some primacy agencies that particle
counters be used to monitor membrane filtrate makes the use of the devices an important concern
in some  states, and a significant factor  in efforts to minimize  microbial risk through integrity
monitoring.

5.4.3  Turbidimeters

Although Adham, et al. (1995) determined that in general conventional turbidimeters are  not as
sensitive as particle counters (or particle monitors) for detecting integrity problems, a recently
developed laser turbidimeter may  have the potential to meet  or exceed the performance  of the
other indirect integrity test methods (Banerjee et al., 1999b, Banerjee  et al., 2000).  Manufacturer
specifications indicate that the laser turbidimeter  is optimized to measure very low  turbidity (i.e.,
in  the  0-1 NTU  range)  and has  a twofold increase  in sensitivity over conventional
turbidimeters,  factors which may make the laser turbidimeter well-suited for membrane filtrate
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monitoring.   Moreover, while  a laser turbidimeter  is  still subject to the same factors that
influence the sensitivity of the  other indirect monitoring devices, it may not be subject to the
various accuracy and precision problems that are endemic to particle counters.

5.5   Regulatory Implications of Integrity Testing

5.5.1   Framework for Minimizing Microbial Risk

As  with  conventional treatment technologies, the allocation of pathogen  removal credit to a
membrane  filtration system by  a primacy agency is driven by  the  ability  of the system  to
minimize  microbial risk.    In   practical  terms,  the  minimization of microbial  risk  means
demonstrating that  the membrane system can adequately remove pathogens and the periodic
and/or continual verification that the membrane barrier  is intact.  Generally,  under the current
regulatory  climate,  any  identifiable  compromise in membrane integrity  must be promptly
addressed, irrespective of the level of microbial risk represented by the integrity breach.  An
overview of the approaches adopted by the state regulatory agencies is presented in Chapter 6.

To  ensure that microbial risk is minimized, there are three criteria that membrane systems have
generally had to satisfy: a theoretical, a  practical, and an operational  criterion.  These are  as
follows:

    1)  Classification of Pore Sizes (theoretical criterion): Pore size classification is an important
       first step in  classifying membranes in terms of the microbial removal capabilities,  as it
       serves as a gauge for the size of pathogens that can be removed.  Typically, the standard
       specifications of the membrane manufacturer are accepted and this criterion is tacitly
       satisfied. However, Cheryan (1998) notes that research has shown that it is common for
       membrane pores at the upper end of the size distribution to be much larger than the rated
       size. This is due,  at least in part, to the lack of an industry standard for determining and
       reporting pore size information for membranes.  Nevertheless,  Cheryan cites additional
       studies showing that membranes may be capable of removing particles as much as three
       times  smaller than the pore size,  and that membranes consistently demonstrate  particle
       removal according to their reported pore sizes when subjected to challenge studies.

    2)  Demonstration of Particle Removal (practical criterion): Once  a pore  size classification
       provides an  indication of the exclusion characteristic of a particular type of membrane,
       microbial challenge studies are conducted to demonstrate this ability.  The acceptance of
       prior  challenge  studies  varies among  utilities  and regulators, which  may  require
       additional demonstration testing as applied to a particular water quality  or an additional
       challenge study conducted under the guidelines of the primacy agency of jurisdiction.

    3)  Verification  of Membrane Integrity (operational  criterion): Even after a membrane has
       been certified by  regulators and  installed, periodic  integrity  testing is necessary  to
       confirm that there are no  compromises that would jeopardize  the allocated pathogen
       removal credits.
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5.5.2  Implications of Current Integrity Test Methods

Integrity testing is  a critical factor  in ensuring the minimization of microbial risk.  Without
methods to  determine whether or not a membrane is integral, there would be no operational
means to verify that a membrane system is continually removing pathogens according to its rated
ability.  However, both the direct and indirect methods of integrity testing have limitations that
inhibit confidence in their ability to  detect integrity problems and which must  be considered in
the overall  context of risk  management.   Pressure-driven  and manual sonic tests  are  not
continuous monitoring methods. Furthermore, the pressure-driven tests are not  on-line methods,
and the more frequently they are conducted the greater the impact on water production.  While
indirect methods are continuous and on-line, they are less sensitive and  some instruments are
subject to errors affecting accuracy  and/or precision.  And although pressure-driven tests (i.e.,
those based on bubble point theory)  are more sensitive than the indirect methods, both share an
inability to detect very small leaks that have implications for microbial risk assessment.

While Adham, et al. (1995) demonstrated that both the pressure hold test and the various indirect
methods (under certain conditions) have the ability to detect holes as small as 600 |j,m in a single
module, an  examination  of the bubble point equation illustrates that the  pressure hold test, as
typically applied to pressurized systems,  can detect integrity breaches on the order of about 0.5
|j,m.  The ability of  the pressure hold test  to detect much smaller holes in these systems is limited
only by the maximum rated TMP of the membranes. It is largely this limitation - the inability of
membranes  to  be tested at pressures that would allow breaches smaller than 0.1   |j,m to be
detected - that prevents UF from receiving significant virus removal  credit.  The vacuum hold
test is similarly limited in its ability to detect breaches smaller than 0.5 |j,m since the maximum
test pressure at which the vacuum test can be applied is -15 psi.

Similarly, indirect integrity monitoring techniques lack the ability to characterize breaches in the
size range of viruses.  Turbidimeters  and particle monitors lack the ability to characterize the size
range of particles that are detected, while particle counters are not widely used to measure the
concentration  of particles in the 0.01  um to 0.1  |j,m range.   However,  particle counters are
commonly used to measure the concentration of particles in the 1 |j,m to 10  |j,m size range and
larger. Thus, particle counters could be used to monitor for breaches in integrity that could pass
particles in the size range  of Cryptosporidium  oocysts and Giardia cysts, but  sensitivity
limitations  of this technology may require a significant number of particle counters to detect a
small number of broken fibers in a rack of modules.  This  may preclude the use of indirect
monitoring techniques as the only means of integrity testing  when removal  credits in excess of
those granted to conventional media filters are considered.  Nonetheless,  indirect methods may
serve as a  useful means of continuous monitoring for larger membrane breaches between  the
periodic application of more sensitive direct integrity tests.

5.5.3  Implications of Potential Future Integrity Test Methods

The  development of an on-line, continuous, direct method  of integrity testing could have  a
substantial  impact on the minimization of microbial  risk with respect to membrane filtration.
Such a test, if sensitive enough, could facilitate the allocation of significant virus removal credit
for UF and perhaps  additional Giardia and  Cryptosporidium  credit for both MF  and UF.
                                          74

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However, even an increase in pathogen removal credits for membrane filtration is unlikely to
shift the long-standing paradigm of multiple barrier protection.  The multiple barrier concept is
grounded  more  in  the  desire for reliable and  consistent treatment rather than  a means of
compensating for inefficient treatment. It is important to note that improved methods of integrity
testing will not enhance the ability  of membranes to remove pathogens, but instead provide a
means of verifying  removal  capabilities that are  demonstrated during challenge testing.   Thus,
improved integrity monitoring may justify increased removal credit, but would not completely
compensate  or eliminate the need for multiple  barriers through the combination  of physical
removal and chemical disinfection.

As new integrity test methods are developed with the  potential to increase pathogen removal
credits for membranes,  it is important that  a standard framework be  developed  for integrity
testing.  Although the idiosyncrasies associated with each proprietary membrane filtration system
may complicate development of this framework, integrity testing standards would lend some
consistency to the process of allocating pathogen removal credits and improve the precision with
which integrity tests are conducted and interpreted.
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6.0   REGULATORY  APPROACHES   TO  MICROFILTRATION   AND
       ULTRAFILTRATION	

6.1  Introduction

As discussed in Section 2.1.1, the current regulation that requires the removal/inactivation of
pathogens during  drinking water  treatment is the SWTR.   This  rule  primarily considers
conventional filtration plants and, to a lesser extent, other media filtration technologies such as
direct,  slow sand, and  diatomaceous earth filtration.  All  other filtration technologies  are
considered  alternate  filtration technologies and are not explicitly  addressed  in  the  SWTR.
Guidance for AFT is  provided in the Guidance Manual for Compliance with the Filtration and
Disinfection Requirements for Public Water Systems Using Surface Water Sources (EPA, 1990),
also referred to as the SWTR Guidance Manual.

In general, AFTs can  be used if the utility demonstrates that the technology, in combination with
disinfection, achieves at least 3-log  Giardia and 4-log virus removal/inactivation.  Utilities are
typically required to demonstrate the ability of AFT to remove pathogens through pilot studies.
However, the SWTR Guidance Manual does make an exception to the pilot testing requirement
for RO, since the technology was considered effective for removal of Giardia and viruses by the
authors of the manual. The other AFTs that were specifically addressed in this manual include
package plants and cartridge filtration units.  Since the application of MF/UF to surface waters
for pathogen removal was  still a  novel concept at  the time the SWTR was developed, these
processes were not mentioned in the rule or the SWTR Guidance Manual.

As discussed in Section  2.2, MF/UF technology has experienced a phenomenal rate of growth
over the past decade, and upcoming regulations that specifically address Cryptosporidium will
continue to drive this  growth. As a result, many states had to develop an approach for permitting
and regulating membrane filtration technologies. The only formal guidance available from EPA
was the AFT provision of the SWTR Guidance Manual,  which does not adequately address the
removal capabilities  and  specific requirements  of MF/UF.   Some states  have chosen to treat
MF/UF as AFT as defined under the SWTR, while other states have developed procedures and
requirements that  are  specific to membrane  filtration technology. This disparity has resulted in a
wide range of regulatory requirements across the states, which  has made it more challenging to
implement this technology in a consistent manner.

Although there is variability among state regulatory  approaches, there are some  common
elements such as, demonstration  of treatment efficacy,  determination of  removal credits, and
integrity monitoring requirements.   Demonstration of treatment efficiency is typically  achieved
through an  initial process evaluation, site specific pilot testing, or full-scale testing.  An initial
product evaluation may include an analysis of existing performance data or certification testing.
Pilot testing is  the  most  common  method of  demonstrating treatment efficiency,  and  is
recommended by the  SWTR Guidance Manual for AFT.  In some cases,  full-scale demonstration
testing is required by the  primacy agency, and typically involves increased  monitoring to verify
that the process performs as  expected.  These three approaches  for demonstrating treatment
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efficacy are not mutually exclusive, and many primacy agencies use these tools in combination
during the permitting process.

The removal credits awarded to a membrane filtration process are based on a variety of factors,
including total removal/inactivation requirements, multiple barrier requirements, experience with
the technology, and results of demonstration testing.  As discussed in Chapter 3, most MF/UF
challenge  studies  demonstrate very high removals of protozoan cysts and cyst sized particles,
often  to below detection  limits.   However, state primacy  agencies do not award  these high
removal credits due to other factors considered when making the determination.  In many cases,
states require a minimum level of chemical inactivation regardless of the demonstrated removal
efficiency  of the process in order to enforce multiple barrier treatment.  Also, states rarely grant
removal credits in excess of the federal requirements for removal/inactivation of pathogens.

Integrity monitoring, using methods discussed in Chapter 4, is typically required to ensure some
level of process performance.  Integrity monitoring requirements for membrane filtration range
from the turbidity monitoring requirements of the SWTR to comprehensive monitoring programs
that utilize a variety of integrity testing techniques.

This chapter provides an overview of the state regulatory requirements for membrane filtration at
the time of this report. A summary of the various regulatory approaches for MF/UF is presented,
followed by a discussion of the key components of these approaches.

6.2  Summary of State Regulatory Approaches

Figure 10, presented in Section  2.2.2.4,  shows the 27 states that have MF/UF plants treating
surface waters or ground water under the direct influence  of surface water at the time of this
report. These states were  contacted regarding their approach for permitting membrane filtration
technologies.  Ohio and Maine were also contacted since these states have begun to develop a
process for permitting this technology, although they did not have any operating MF/UF systems
at the time.  The remaining 21  states were not contacted since there were no MF/UF plants
operating  in these states and no information was  available regarding their approach towards
permitting membrane filtration.

Table 14 presents a summary of the state regulatory requirements for membrane filtration.  The
table shows the number of MF/UF  plants  in the state; the maximum removal  credits awarded for
Giardia, viruses,  and Cryptosporidium;  minimum  chemical  inactivation requirements;  pilot
testing requirements; and  integrity monitoring requirements.   This information represents the
regulatory status of membrane  filtration  at the time  of this report, and many of the primacy
agencies indicated that their process is evolving as more  experience with  this relatively new
technology is  developed.  Additional  information on the policies  of a particular state may  be
obtained by contacting a representative from that state's drinking water program.  A list of state
drinking   water  programs  can  be  found  on  the  Association  of State  Drinking Water
Administrators (ASDWA) homepage (www.asdwa.org).
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Table 14. Summary of State Primacy Agency Regulatory Requirements
State
AK
AZ
CA3
CO
CT
FL
HI4
ID5
KS
ME
MA
Ml6
MO
NV
NJ
NY
NC
OH
# MF/UF
Plants
8
2
28
8
2
1
7
4
2
0
3
8
1
4
1
2
2
0
Maximum Removal
Credits1
Giardia \ Virus
Crypto
No specific credits granted
3
4
0.5 MF
4 UF
0.5 MF
4 UF
NA
4
No specific credits granted
2.5
2.5
1
3
0
0
0
0
NA
NA
NA
NA
No specific credits granted
1.5
2
3
2.5
2.5
0
0
0
0
0
NA
2
NA
NA
NA
No specific credits granted
No specific credits granted
No specific credits granted
2.5
0
NA
Minimum Chemical
Inactivation Requirements
0.5-log Giardia inactivation
Balance of SWTR
requirements
Maximum of 0.5-log Giardia
or 2-log virus inactivation
0.5-log Giardia inactivation
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
0.5-log Giardia inactivation
Balance of SWTR
requirements
0.5-log Giardia inactivation
Balance of SWTR
requirements
Pilot Testing
Requirements
Some cases
Not required
Some cases
Not required
All cases
All cases
Some cases
Some cases
Some cases
All cases
All cases
Some cases
All cases
All cases
All cases
Some cases
Some cases
All cases
Integrity Monitoring
Requirements2
Not required
Varies - monitoring
requirements are linked to
removal credits
Varies - may include PC/PM
and/or physical integrity testing
Continuous - may include
PC/PM or pressure drop
Not required
Not required
Not required
Periodic - physical integrity test
Continuous - pressure drop
Periodic - physical integrity test
Not required
Not required
Continuous - PC/PM
Periodic - physical integrity test
Not required
Not required
Periodic - physical integrity test
Not required
Periodic - physical integrity test
Continuous - PC/PM
Periodic - physical integrity test
                                                   79

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Table 14. Summary of State Primacy Agency Regulatory Requirements (continued)
State
OK
OR
PA7
SD
TN
TX
UT
VA
WA
Wl
WY
# MF/UF
Plants
2
3
4
2
1
5
2
12
2
4
1
Maximum Removal
Credits1
Giardia \ Virus
Crypto
No specific credits granted
2.5
3
2.5
3
3
3
2
3
3
0
4UF
0
0
0
0.5
OMF
1 UF
OMF
4UF
OMF
3UF
NA
2
NA
2
2
NA
NA
3
3
No specific credits granted
Minimum Chemical
Inactivation Requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
Balance of SWTR
requirements
0.5-log Giardia inactivation
Balance of SWTR
requirements
Balance of SWTR
requirements
Pilot Testing
Requirements
All cases
Not required
All cases
All cases
Some cases
All cases
Some cases
Some cases
Some cases
All cases
Some cases
Integrity Monitoring
Requirements2
Not required
Not required
Continuous - PC/PM
Periodic - physical integrity test
Not required
Not required
Continuous - PC/PM/LNTU
Periodic - physical integrity test
Continuous - PC/PM
Periodic - physical integrity test
Continuous - PC/PM
Periodic - physical integrity test
Periodic - physical integrity test
every 4 hours
Periodic - physical integrity test
every 8 hours
Not required
1 . These are the maximum removal credits awarded to a membrane filtration process, and lower credits may be awarded in some cases.
2. All plants are required to monitor turbidity under the SWTR - additional integrity monitoring requirements are shown in this table.
3. California awards removal credits based on the results of microbial/particulate challenge studies for specific products.
4. Hawaii is considering increasing the Giardia removal credit to 3-log. A plant in HI indicated that it was awarded 2.5-log credit for Giardia and Crypto.
5. A plant in Idaho indicated that it was awarded 3-log credit for Giardia and Crypto and 4-log credit for virus.
6. A plant in Michigan indicated that it was awarded 3.5-log credit for viruses.
7. Requirements for Pennsylvania are based on the application of UF to finished water in Pittsburgh. Different requirements may apply to MF/UF applications treating raw or
pretreated surface waters, but information was not available from these sites.
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The maximum  removal credits awarded to membrane filtration processes are shown for each
state in Table 14, although site specific factors may lead some states to award lower credits than
those  listed.  The removal credits reported in  Table 14 are applicable to both MF and UF
processes, except for viruses, where  different removal credits may  be awarded for the two
technologies. Eight of the 29  states do not award specific removal credits to membrane filtration
processes; rather the state evaluates the entire treatment plant as a whole to determine whether or
not the combined barriers of removal and disinfection meet the SWTR requirements.

The Giardia and Cryptosporidium log removal credits granted  to  membrane filtration are
summarized in  Figure  14.  In general, states did not  make a distinction between MF and UF
processes when determining removal credits for these pathogens. This is consistent with the fact
that the exclusion characteristic of both MF and UF membranes  is  small enough to provide
removal to below the detection limits of these organisms.  Of the  21  states that have awarded
specific removal credits to  MF/UF, California awards up to 4-log Giardia  credit, nine states
award up to 3-log Giardia credit, seven states award up to 2.5-log Giardia credit and four states
award 2-log Giardia credit or less. Only seven  states  have awarded specific  removal  credit for
Cryptosporidium, four of which grant the 2-log Cryptosporidium removal credit required by the
recently promulgated IESWTR and proposed LT1ESWTR (63 FR 69477, 65 FR 19045).  Two
states grant up to 3-log  removal credit and California grants up  to 4-log removal  credit for
Cryptosporidium.

The virus log removal credits granted to membrane filtration are summarized in  Figure 15, and
unlike  the case  for Giardia and Cryptosporidium removal,  some  states  do make a distinction
between MF and UF processes for the case of virus removal.  This approach is  consistent with
the results of several studies,  some of which are summarized in Chapter 3, which demonstrate
virus removal to below detection limits by most membrane processes classified as UF,  compared
to the  variable  removals observed for membrane processes  classified as MF.  Virus removal
credits awarded to UF  processes range from 0-log to  4-log, while the maximum virus removal
credit awarded  to a MF process is only 0.5-log.   The majority of states did not grant  any  virus
removal credit to either MF or UF processes. One of the primary reasons that full virus removal
credit  is not typically granted  is the inability  of integrity  monitoring techniques  to  detect
breaches or pores that could  pass viruses,  as  discussed in Chapter  5.   Also,  several states
indicated that other treatment requirements result in  disinfection levels that exceed  the  4-log
virus inactivation requirement.

The  removal credits  shown  in Table 14  do not meet the 3-log Giardia  and 4-log  virus
removal/inactivation requirements of the SWTR, with the possible  exception of UF applications
in California and Arizona.   In cases where full removal  credits are not awarded,  chemical
inactivation would be required to make up the balance of the SWTR requirements. Furthermore,
Alaska, California,  Colorado, New Jersey, North Carolina,  and  Washington have  minimum
chemical inactivation requirements regardless of the removal credits awarded to any process.
The end result  is that almost every  membrane filtration plant operating in  these 29 states is
required  to provide  some level of primary disinfection with  chemical  inactivation,  which is
consistent with the multiple barrier approach to drinking water treatment.
                                          81

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              22
                                                       Giardia
                                                       Cryptosporidium
                                o
           NSC
1.0
 (NSC: no specific credit granted)
1.5       2.0       2.5
  Log Removal Credit
            3.0
           4.0
Figure 14.  Maximum Log Removal Credits for Giardia and Cryptosporidium for 29 States
              NSC
    0.0
     0.5
1.0
3.0
4.0
                             Virus Log Removal Credit
 (NSC: no specific credit granted)
Figure 15.  Maximum Virus Log Removal Credits for MF and UF for 29 States

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Pilot testing requirements have been consolidated into three categories in Table 14: not required,
required in some cases, or required in all cases.  Thirteen of the 29 states (45%) require pilot
testing in all cases, 13 states (45%) require it in some cases and 3 states (10%) do not require
pilot testing for membrane filtration.  States that do not require pilot testing or require testing in
only some  cases typically  offer alternatives for demonstrating process  performance  in lieu of
pilot studies, such as prior tests conducted at another site or full-scale demonstration testing.

Integrity testing requirements are summarized in  Table  14  using five categories: not required,
continuous   testing,  periodic  testing, both  continuous  and  periodic testing,  or  variable
requirements.  Figure  16  summarizes  the integrity monitoring requirements for the 29  states
contacted  during this  project.   Continuous monitoring  typically uses one  of the  following
methods: particle  counting (PC),  particle monitoring (PM),  laser turbidimetry (LNTU),  or
pressure drop across  the membrane,  while periodic monitoring typically consists of physical
integrity testing using the pressure hold test. One state requires only continuous monitoring, five
states require only periodic, physical integrity testing,  seven states require both continuous and
periodic monitoring, and two states determine the integrity monitoring requirements on a  case-
by-case basis.   Fourteen  states  do not require any  type of integrity  monitoring beyond  the
turbidity monitoring required under the  SWTR.
    16

    14 1
V)
3  12-

§  10 :
n-
2    81
•Q    /-
I
Z    4

      2

      0
                  14
                                                              7
                                 1
                None     Continuous    Periodic        Both       Variable
                            Integrity Monitoring Requirement
Figure 16. MF/UF Integrity Monitoring Requirements for 29 states

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In this summary, the components of state regulatory approaches for membrane filtration have
been discussed independently; however, it is important to consider how these components work
together to establish a comprehensive framework for this technology.  For example, states that
require utilities to develop an integrity monitoring program were  found to  be more  likely to
award higher removal credits to  a membrane filtration process.  The  use of sensitive integrity
monitoring techniques provides increased confidence in the membrane barrier, thus reducing the
need to rely entirely  on chemical inactivation as a safeguard.  In the  following sections, these
components will be discussed in greater detail, including specific examples that demonstrate the
synergy between the various components.

6.3  Initial Product Evaluation

Due to the proprietary nature of membrane filtration systems and  limited experience  with the
technology, most states require MF/UF systems to undergo an initial product  evaluation prior to
design and construction of a facility. A product evaluation can range from a desktop analysis of
manufacturer specifications and data from previous studies to a testing  and certification program
administered by the state or a third party.

At  a minimum, most states require that chemicals  and materials  that come in contact with
drinking water meet National Sanitation Foundation (NSF) Standards 60 and 61, respectively.
These standards are in place to ensure that harmful  chemicals are not introduced into drinking
water through  either direct  addition or  leaching.   Both membrane materials  and  chemical
cleaning agents are covered  under  these standards.  Many membrane systems and proprietary
cleaning chemicals are certified under the appropriate NSF standard.  However, some states have
reported problems due to  a  lack of certification  for  a  specific product and had to  resort to
alternate criteria to verify that the  material in question met the intent of the NSF standards.

As  part of the initial product  evaluation, most states require manufacturers to supply data for the
proposed membrane system, including system specifications, basic design information, pore size
distribution, and absolute/nominal pore size cutoff. A few states require data beyond this basic
information.  For  example, Virginia requires certification that the membrane  has an absolute
cutoff of 1 |j,m  or less, where the  absolute cutoff is demonstrated by 7-log removal.  As another
example, Wisconsin requires  manufacturers to supply theoretical calculations  relating the results
of  integrity testing to a  known number  of broken fibers.  As discussed in Chapter  5,  an
understanding  of this fundamental  relationship  is  necessary to  establish  control limits for
integrity test results that are based on risk of microbial passage.

In addition to manufacturer information, data from previous demonstration studies may be used
during initial product  evaluation, and some states will use this information in lieu of site specific
pilot studies or certification  studies.  For example, Tennessee used existing  data to permit the
first installation in the state without pilot testing.  During initial product evaluation, Arizona has
considered removal credits  awarded to a  specific membrane filtration  process by other state
agencies.  Also, a number of states used  information developed by California and Virginia to
support permitting of the first installations in their respective states.
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Some states require products to be certified within the state or by an independent third party
before a system can be approved for use in the state.  The objective of certification testing is to
demonstrate  the ability  of a  membrane  process to  remove pathogens  such  as  Giardia,
Cryptosporidium, and  viruses.  This is typically  accomplished through microbial or particulate
challenge studies.   Additionally,  fiber-cutting studies  may  be performed during certification
testing to evaluate the ability of integrity monitoring procedures to detect a failure.

There are a variety of general certification programs used by various state agencies. Both Alaska
and Idaho require demonstration of Giardia removal by membrane filtration through third party
testing according to the Western States Protocol (Bruce Barrett & Associates, 1992). Wisconsin
requires bench-scale testing to demonstrate pathogen removal for each proprietary membrane
system used in the state.  In some cases, states  will allow a pilot study conducted at the first
installation in the state to be used for the purpose of certification.  For example, manufacturers
have used pilot studies conducted at the first installations in California, Virginia, and Texas for
the purpose of obtaining  certification  within each respective state,  in addition to  meeting the
requirement to  perform site specific studies.  Some states that have just started to address this
technology are  requiring all utilities to  conduct site specific pilot tests to demonstrate pathogen
removal, effectively rendering these tests certification studies.

In addition to state specific certification programs, there are independent, third party certification
programs.  A national  certification program is attractive since  it  provides a  standard, transparent
testing program that can be used by all manufacturers,  regulatory agencies and utilities for the
purpose of process certification.  The NSF ETV program is an example of a national program
that  tests membrane filtration processes according to a  standard  protocol.   For membrane
processes, the NSF  ETV program evaluates removal  of Giardia cysts and  Cryptosporidium
oocysts through challenge studies.  The results are published  in a report and made available to
stakeholders and other interested parties.  The LT1ESWTR (IV, A, 1, a,  ii) suggests the NSF
ETV program as a potential means of verifying the performance of membrane technology (65 FR
19045).

Some states have indicated  that they would consider using NSF ETV certification to  meet the
requirements of their own certification program or pilot testing requirements.  Use of NSF ETV
results in lieu of site specific pilot testing is especially attractive for small systems that may find
MF/UF technologies  cost prohibitive  with  the  added expense  of an extended  pilot study.
However, a few states  have indicated that they may not  be willing to rely solely upon NSF ETV
certification for process approval.  One state specifically expressed a concern over the role that
manufacturers have  played in  the  development  of acceptance criteria  for NSF ETV testing.
Furthermore, NSF ETV testing  does not replace the need for site specific pilot testing conducted
to develop design and operational criteria as well as demonstrate the economic feasibility of
implementing the technology.   Pilot  testing  conducted for  this purpose  is discussed in  the
following section.
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6.4   Pilot Testing Requirements

As discussed in Section 6.2, 26 of the 29 states contacted during this project require pilot testing
in at least some cases.  The purpose of pilot testing varies from  state to state, but in general the
objectives of testing can be divided into two broad categories: testing to demonstrate pathogen
removal or testing to assess site  specific performance of the MF/UF  system.   The former
objective  is  typically  associated  with  certification testing,  and  many  states that require
demonstration  of pathogen removal during pilot  testing use these results for the purpose  of
certification or  determining  removal credits.  For example, pilot  testing at  some  of the first
installations in California, Virginia, and Texas were used for the purpose of product certification.
States that require pilot testing  to  assess site specific performance are more concerned with
process feasibility and system operation.  Some states require certification testing  of proprietary
systems as well as site specific pilot testing to demonstrate process feasibility.

Most pilot testing required by state agencies is conducted for the purpose of evaluating site
specific design  and  operational issues.    These  issues  may include  the  determination  of
pretreatment  requirements to control fouling, acceptable fluxes,  and cleaning  intervals and
efficiencies.   For example,  Texas uses pilot testing  to determine the  adequate  level   of
pretreatment to ensure acceptable productivity under a range of influent water quality conditions.
Several states  use the  results  of  pilot testing  to establish  constraints  on these  operating
parameters.  At  some of the early MF installations in California, the state established a TMP that
triggered chemical cleaning, treating TMP analogous to  headloss in a media filter.  California
also uses pilot testing to establish the maximum flux at which a specific product can be operated
at full-scale.    States  that  use  pilot study results  to  establish  operational  criteria for MF/UF
typically provide utilities with the  option to conduct additional testing to demonstrate that the
process can safely operate outside of the previously established operational criteria.

Thirteen states contacted during  this project require pilot  testing in all cases.  Many of these
states treat MF/UF as AFT as defined in the SWTR Guidance Manual which recommends pilot
testing these processes (EPA, 1990).  However, some states with a more progressive view  of the
technology also require pilot testing in all cases.  For example, Texas requires pilot  testing  to
gather critical process design data, and Wisconsin requires testing to further demonstrate particle
removal and  determine full-scale operating parameters. Also, there are at least two states, New
Jersey and Ohio, which require  all new drinking water treatment  facilities to be  pilot  tested
regardless of the technology being implemented.

Thirteen states require  pilot testing in only some cases.   In general, these states require new
products to be piloted at least once in the state, and after  the technology has been demonstrated,
other utilities in the state using the same technology may not be  required to conduct pilot studies.
States such as California, Virginia, and Hawaii that have been dealing with membrane filtration
for several years initially  required  all  utilities installing new membrane filtration facilities  to
conduct pilot testing prior to construction; however, as these states gained experience with this
technology, the pilot  testing requirements were relaxed.  Under certain conditions,  all three  of
these states may waive the pilot testing requirement if the membrane system under consideration
has already been tested in the state.  States  with fewer  installations  have adopted  a similar
philosophy to the pilot testing requirement.  For example, Kansas, Idaho, and Michigan require
                                           86

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the first installation of a given proprietary system to be pilot tested but may waive the pilot
testing requirement for subsequent installations using the same technology.

Some states offer alternatives to pilot testing for the purpose of verifying system performance.
Alaska  and Washington  allow full-scale testing  to  be used for the purpose  of  process
demonstration.   Although,  in the case of Washington,  full-scale testing has historically been
limited to very small systems proposing to install bag or cartridge filtration where the size of the
pilot system was comparable to the size of the full-scale plant. Virginia has a mandatory, 30-day
shakedown period during which increased monitoring is required, and this full-scale evaluation
period may be used in lieu of pilot testing in some cases.  Arizona does not require pilot testing,
but does require plants to go through a  startup phase during which increased monitoring and
increased chemical disinfection are required.

Only  three  states do not require  pilot testing of  membrane filtration processes - Arizona,
Colorado, and Oregon. These states cited two primary reasons for not requiring pilot studies: the
large amount of existing data demonstrating effective pathogen removal by MF/UF, and  the fact
that many utilities will conduct pilot testing to develop design information and bidding criteria
regardless of the state requirements.  In fact,  most utilities in states without a pilot testing
requirement did perform pilot studies for use in membrane procurement and system design. The
risk of economic failure of the system, given the cost of the technology, drives the decision to
conduct pilot studies as opposed to regulatory requirements.

6.5   Determination of Removal Credits

As discussed in Chapter 3, there is a substantial amount of data demonstrating that  MF/UF
membranes  can  achieve  pathogen  removal   to  below detection limits if the  exclusion
characteristic of the membrane  is smaller than the  size of the target  organism,  assuming an
integral membrane system.  Much of this data was obtained from bench-  or pilot-scale microbial
challenge studies in which seeded concentrations of microorganisms in the membrane feed were
much higher than typical pathogen concentrations in surface  waters.  The high  levels of seeded
organisms result in log removals as high as 5-, 6- and 7-log.  Researchers have observed that log
removal of  pathogens by an integral membrane process is  a function  of the  concentration of
organisms in the influent (Jacangelo, et al., 1997).  In a similar manner, the use of seeded
surrogates such as  particles or indigenous spores  results  in  high log  removals since the
concentrations of these surrogates are higher than naturally occurring pathogen levels.

The log removal credits awarded by state agencies, summarized  in Section 6.2,  are less than the
log removals  observed during  pathogen challenge studies.   Many  states  have  adopted  a
conservative approach to awarding removal  credit to provide a  factor of safety on the process.
However, the most common reason  for this approach is the reluctance of most  state agencies to
award removal credits beyond the federal SWTR requirements of 3-log Giardia and 4-log virus
removal/inactivation to any technology.

Under the federal SWTR, a well operated conventional treatment plant  that meets the turbidity
requirements of the rule may receive up to 2.5-log Giardia and 2-log virus removal credit. The
remaining  0.5-log  Giardia and 2-log  virus  credit  must be  achieved through  chemical
                                          87

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disinfection,  and some states award less  than  the  suggested removal  credit to conventional
filtration and require higher levels of disinfection.  Removal credits are awarded in this manner
to enforce the long-standing practice of multiple barrier protection through a physical barrier and
a disinfection barrier.   The  physical  treatment  barrier is  provided by  the combination  of
coagulation,  sedimentation, and filtration.   The disinfection barrier is  provided through the
application of chemical disinfectants or potentially ultraviolet irradiation.

Relative to the benchmark of 2.5-log Giardia removal credit for conventional  treatment, Figure
14 indicates that 10 states treat MF/UF as a superior barrier to pathogens and award up to 4-log
Giardia removal credit.  Seven  states  award up to 2.5-log removal credit, essentially treating
membrane filtration as equivalent to conventional filtration with respect to pathogen removal.
Finally, four states  (Hawaii, Maine,  Massachusetts,  and Virginia) award less than 2.5-log
removal credit to MF/UF, although there are special circumstances in each case. Hawaii's initial
experience with  membrane filtration dealt with unfiltered systems that were required to install
filtration technology.  These utilities had more than  3-log  Giardia disinfection capacity which
allowed the state to be conservative and grant  only 1-log of Giardia removal  credit to MF/UF;
however, the state is considering increasing the credit to 3-log.  Maine does not have any full-
scale  MF/UF plants,  and  currently treats  MF/UF as  an AFT along with bag  and cartridge
filtration, which are granted 1.5-log Giardia removal credit.  Virginia, which was one of the first
states to permit membrane filtration processes, grants 2-log Giardia removal credit to MF/UF but
is in the process of revising the requirements for membrane plants and may increase the removal
credits.  Eight states with operating MF/UF facilities do not award  specific removal credits  to
membrane filtration, but  rather evaluate all treatment barriers as a system to determine whether
or not the SWTR requirements are  met.

An  evaluation of the maximum removal credits listed in Table 14 shows that currently only two
states, Arizona and California, would potentially award all removal credits required under the
SWTR to an UF process.  However, California does  require some level of chemical inactivation
regardless of the removal credit  awarded to the process. (The Pittsburgh plant in Pennsylvania
was also awarded full removal credits for the IESWTR; however, this is a unique application  in
that UF is being used to re-treat  finished water.)  In all other cases, states require  MF/UF plants
to provide at least enough chemical disinfection to meet the balance of the SWTR requirements.
This typically amounts to 4-log virus inactivation and/or 0.5-log Giardia inactivation, but is  as
high as 2-log Giardia inactivation  in Hawaii.  Furthermore, Alaska,  California, Colorado, New
Jersey, North Carolina,  and Washington  require a minimum  level of chemical inactivation
regardless of the technology used or the associated removal credits.  In some cases, the primacy
agencies in these states may grant the complete 3-log removal credit for  Giardia, yet may still
require the plant to provide some level of  Giardia  inactivation.  For states  with a  minimum
inactivation requirement,  the minimum level is typically  0.5-log of Giardia inactivation, which
will provide in excess of 4-log virus inactivation when free chlorine is used as the disinfectant.
Other  minimum  inactivation   requirements  that have been  implemented,  or  are  under
consideration by state  agencies, include 0.25-log for Giardia and 2- to 4-log for virus.

These minimum disinfection requirements impact  the use  of MF  and UF as compliance
technologies for the DBF regulations. In cases where membrane filtration is awarded most or all
of the required removal credit, the  plant may be able to reduce free chlorine contact time to meet

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the DBF  MCLs.  However, when  a high post-filtration  contact time  is necessary to meet
disinfection requirements,  significant levels of DBFs can form, limiting the potential of MF/UF
as a DBF control  strategy.  Many researchers  suggest that some disinfection after MF/UF is
necessary  to control bacterial regrowth on  the filtrate side of the membrane (AWWA,  1999).
However,  the different inactivation  requirements  of  state agencies  demonstrate the range of
opinions with respect to the level of disinfection necessary after membrane filtration, and in a
more general  sense, how the multiple barrier concept applies to membrane filtration.

The manner in which primacy  agencies assign  removal credits also  varies  from state to state.
Some states will assign the same removal credits to all membrane filtration process, while others
will assign the same removal credits to all plants using  a specific proprietary system. However, a
number of states make case-by-case determinations  regarding removal  credits, regardless of
whether or not the system is being used at another plant in the state.  These removal credits are
often based on the results of microbial or particulate  challenge studies; however, since removal
to below detection limits is typically observed in these studies, most  MF/UF plants in the state
end up  receiving the same or similar credits.  A few states consider additional factors when
determining removal  credits. For example, Arizona will award higher removal credits to utilities
that use more  sensitive and reliable integrity monitoring procedures relative to those that rely on
turbidity monitoring.   In  at least one case, California considered operating parameters when
assigning removal credits and reduced the virus removal credit when the plant elected to operate
at a higher flux. Although there are exceptions, by far the general practice has been  to award
partial  removal  credits  to  MF/UF and  require  plants to make up the balance  of the SWTR
requirements through inactivation.

As discussed  in  Chapter 2, the IESWTR will require most surface water plants to achieve 2-log
Cryptosporidium removal,  and the  LT2ESWTR could  require plants with  high influent
Cryptosporidium concentrations to achieve up to 5.5-log Cryptosporidium removal/inactivation.
Figure 14 shows that only seven of the 29 states  have awarded removal credits to membrane
filtration for Cryptosporidium at this time.  Massachusetts, Pennsylvania,  Tennessee, and Texas
have awarded the 2-log credit required under the  IESWTR to membrane filtration; Wisconsin
and Washington have granted 3-log credit;  and  California has  granted up to 4-log credit.  The
Agreement in Principle for the LT2ESWTR currently proposes  granting a  minimum 2.5-log
Cryptosporidium removal  credit to membrane processes if specific performance criteria are met
(65 FR 83015).  State primacy agencies will  need  to address  Cryptosporidium  removal  by
membrane filtration since  it is likely that a number of utilities will consider this technology to
comply  with  the upcoming regulations.  States will  also need to make a determination  with
respect  to Cryptosporidium removal  for existing  membrane plants,  and in some  cases  may
require additional testing.

6.6  Integrity Testing Requirements

As discussed  previously, states rarely award all of the removal credit required under the SWTR,
and require some level of chemical  disinfection.  One reason that multiple barrier protection is
required for membrane filtration is the concern regarding membrane integrity.   Even though
membranes have demonstrated  very  high levels of pathogen removal, there  is a potential for
microorganisms  to contaminate  the filtrate if there  is an integrity breach.  Chemical disinfection
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can serve as an additional barrier in the event of a failure.  However, integrity monitoring can be
used to verify the integrity of the system and thus reduce the need for a large disinfection barrier.

At the time of this report, 14 of the 29 state agencies contacted did not require integrity testing.
These states  do require turbidity monitoring,  but as  discussed in  Chapter  4,  current turbidity
technology lacks the sensitivity to detect small breaches in integrity that are of concern.  The
remaining 15  states require periodic physical  integrity  testing  and/or continuous integrity
monitoring. All states that require periodic physical integrity testing stipulate use of the pressure
hold test. States that require continuous integrity monitoring permit use of one of the following
methods: particle counting,  particle monitoring, laser  turbidimetry, or  pressure drop across the
membrane.   At the time of this report,  only  Texas  has expressly permitted  the use  of laser
turbidimeters for membrane integrity  monitoring;  however, other states are  considering this
monitoring technology.

As  discussed in Section 4.2.1, the pressure hold test is  a  direct method of verifying system
integrity; however,  it requires  the system to be taken off-line, and thus can only be used for
periodic  testing.  Twelve states require periodic integrity testing using the  pressure hold test,
some of which have established a testing frequency. Washington requires pressure hold testing
at 4-hour intervals to be consistent  with the  4-hour turbidity monitoring  requirement of the
SWTR and to compensate for the lack of a continuous monitoring technique capable of detecting
breaches that are of concern. Wisconsin requires pressure hold testing at 8-hour intervals. Most
states that require pressure hold testing specify daily testing, and  a few require  less frequent
testing.  For example, Texas and Oregon require  pressure hold testing to be conducted at weekly
intervals, and Kansas requires testing  to be performed when the  system is taken off-line for
cleaning.  Seven of the twelve states  that require periodic pressure hold testing  also require
continuous monitoring.

Continuous monitoring provides a real-time measure  of system performance, but the methods
currently available  only provide an  indirect assessment of membrane integrity.   Eight states
require continuous testing beyond the turbidity  monitoring requirements of the SWTR, and six of
these states require particle counting, particle  monitoring, or laser  turbidimetry in the case of
Texas.  One  state, Kansas, requires pressure drop monitoring while Colorado allows the use of
particle counting, particle monitoring,  or pressure drop,  and is considering  laser  turbidimetry.
States that require continuous monitoring typically require one monitoring  unit per membrane
rack,  or in some cases only require monitoring of the combined filtrate.

In addition to periodic and continuous  testing,  most membrane filtration plants need to  perform
diagnostic testing to isolate problems  identified during integrity testing. As discussed in Chapter
4, methods commonly used for diagnostic testing include  the pressure hold test, the bubble point
test  and sonic testing.   A few states do  require plants to  conduct periodic diagnostic test
independent of routine integrity monitoring results.

Regardless of the integrity monitoring technique used, it  is necessary to establish control limits
that trigger a specific action when exceeded.  For periodic testing using the pressure hold test,
manufacturers  often  specify the pressure decay rate below which the system is considered
integral;  however, as  discussed  in Chapter 5, there are a number of factors that impact the
                                           90

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relationship between pressure hold test results and risk of microbial passage.  A few states, such
as Wisconsin and Virginia, require manufacturers to provide a theoretical basis for the specified
control level.  The  theoretical relationship between the results of the pressure hold test and the
number of broken fibers can be used to establish control limits that ensure the system is capable
of achieving the removal credit granted by the primacy agency.

For continuous testing using particle counters or particle monitors,  relative counts are typically
used to establish control limits due to the difficulties associated with measuring absolute particle
counts.  In order to develop control  levels  for relative particle counts, it is necessary to establish
a baseline during operation  with  integral  membranes, where  the integrity is typically verified
through the pressure hold test. A control  level  is established at some value above the baseline,
and particle counts above this control level trigger a response.   Since there is not a standard
methodology for establishing a control limit for particle counts, states typically set the limit at a
conservative value.

The  individual  tools  available  to  monitor membrane  integrity  can  be  combined  into  a
comprehensive monitoring program.  Two states that have developed such programs are Texas
and Wisconsin.  Texas based  its monitoring  program on continuous  particle counting  and
requires particle counters on each rack of membrane modules.  A baseline particle count level is
established with integral membranes (verified through direct integrity testing), and the  control
limit is set at two standard deviations above the  mean baseline value. If the particle counts from
a rack of membranes exceed the control limit, a direct integrity test must be conducted on the
rack of membranes,  and sonic  testing is used  isolate compromised modules as necessary.
Utilities are also required to conduct direct integrity testing once per week independent of the
particle count monitoring.

Wisconsin's monitoring program is based on the pressure hold test conducted  at 8-hour intervals.
Fiber-cutting studies  are performed at all full-scale  installations to determine the relationship
between pressure hold  test  results and the number of cut fibers, and to ensure that the test is
sufficiently  sensitive  to detect a  breach that would  compromise the level  of  removal credit
awarded with a  1-log  factor  of safety.  This relationship is used to establish two control limits for
pressure decay rates during  pressure hold testing.  Results below the lower control limit  require
no action. Results between the lower and upper control limits require sonic testing of the  suspect
modules.  Results above the upper control  limit require the suspect modules to be taken off-line
for repair/replacement.  Utilities are also  required  to  conduct sonic testing  every 30-days
independent of the pressure hold test results.

The  comprehensive monitoring programs for  Texas and Wisconsin  demonstrate  how either
continuous indirect monitoring  or direct  integrity testing can be used to evaluate membrane
integrity and establish control limits for the monitoring results.
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6.7   Summary

The results of this state survey demonstrate the significant differences that exist among various
approaches to regulating MF/UF for pathogen removal.  There are a range of requirements with
respect to product certification and pilot testing.  At one extreme, states rely on existing data and
do not require further demonstration of product  performance.  At the other end of the spectrum,
some  states  require  product certification,  site specific  pilot  testing  and  full-scale process
demonstration.  With respect to removal credits, states awarded 1- to 4-log  Giardia removal
credit for MF and UF membranes, with most states granting 2.5- or 3-log credit. With only three
exceptions, states did not award virus removal  credit to MF processes, and in no case was the
virus  removal credit  greater than 0.5-log.   Seven states  awarded virus  removal credit to UF
membranes,  with credits  ranging from  0.5-  to  4-log.   Only  seven   states  have awarded
Cryptosporidium removal credit to membrane filtration, with credits of 2-, 3-, or 4-log. Eight of
the 29 states did not award specific removal  credits  to membrane filtration  processes.   A
commonality among the various regulatory approaches is  that in almost all cases some level of
chemical disinfection was required for MF/UF filtrate.

There  were also significant differences in the monitoring required by different states.  Fourteen
of the 29 states did not require any integrity monitoring for membrane filtration plants aside from
turbidity.  Of the remaining 15  states, seven require both continuous indirect monitoring and
periodic  direct integrity testing,  five require  only direct integrity  testing,  one requires only
continuous indirect monitoring,  and two approve integrity monitoring plans  on a case-by-case
basis.  All states that require direct integrity testing stipulate use of the pressure hold test, while
states that require continuous indirect  monitoring specify particle counting, particle monitoring,
laser turbidimetry, or pressure drop monitoring.

Much of the variability in state requirements for membrane filtration is a result of  factors such as
different approaches to multiple barrier treatment, different levels of experience with membrane
processes, the lack of standardization in this technology  field, and  a lack of formal guidance
from USEPA that adequately addresses this technology.  This variability present  challenges for
the implementation of this technology.

During this project, several states raised outstanding issues related to the regulation of membrane
filtration for pathogen removal, including:
    •   Failure to adequately address membrane filtration in the federal regulations

    •   Consistent determination of removal credits for membrane filtration processes

    •   Defining appropriate multiple barrier protection for a membrane filtration process

    •   Reliability, sensitivity and transparency of integrity testing methods

    •   Increased understanding  of the relationship between integrity testing results and a breach
       in integrity and risk of microbial passage
    •   Appropriate use of particle counting, particle monitoring and turbidity monitoring in an
       integrity monitoring program
                                           92

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   •   Product certification,  and  the  impact  of certification on  site  specific  pilot testing
       requirements
   •   Appropriate cross-connection control for CIP systems

   •   Longevity of membrane elements, and changes in performance with time

   •   Operator certification for membrane filtration processes

Of these unresolved issues, one  of the most important may be the first, the failure of federal
regulations to adequately address  membrane filtration technology.   If this issue were to be
resolved in a sound and defensible manner, it would go a long way towards resolving some of
the other outstanding issues listed above.   This  would ultimately lead to greater consistency
among the various regulatory  approaches and would make it easier to  implement membrane
filtration technology for pathogen removal.
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7.0   UTILITY PRACTICES
7.1   Introduction

A representative sample of twenty-four utilities was selected from the installation lists provided
by  MF/UF  manufacturers and contacted to  obtain  information  regarding  their membrane
facilities.  This information included operating parameters and the factors that contributed to the
decision to utilize membrane filtration.  Utilities were selected based on location (i.e.,  state),
installation date, and the manufacturer of the proprietary membrane  system.  The information
received from the utilities is summarized in Table 15, while the decision drivers and operational
practices are discussed in more detail in Sections 7.2 and 7.3, respectively.


7.2   Decision Drivers

The utilities  contacted cited a number  of reasons for choosing membranes as part of their
respective treatment schemes, ranging from regulatory considerations to addressing consumer
concerns.  The drivers for installing membrane filtration are listed below in order of frequency
cited.

    1)  Membrane  filtration  facilitates   compliance  with  existing  and   future  regulatory
       requirements

    2)  An intact membrane provides an absolute barrier to protozoan  cysts and bacteria, and in
       the case of UF, can achieve significant virus removal

    3)  Membrane filtration systems are  easy to operate, less  susceptible to changes in source
       water quality, and highly automated

    4)  The footprint for a membrane plant is small compared to other technologies

    5)  Membranes provide another treatment barrier to protect public health

    6)  The cost of membrane filtration is competitive with other technologies

    7)  Membranes are economical for unfiltered systems that are concerned about losing their
       unfiltered status

    8)  Membrane filtration is an effective pretreatment for nanofiltration and reverse osmosis

    9)  Membrane filtration alleviates consumer concerns regarding source water quality

Regulatory requirements were most frequently cited  as a reason for installing MF/UF technology
by the utilities contacted. Several utilities were concerned that their existing  facilities would not
be sufficient to meet the CT (disinfectant residual  x contact time) requirements of the SWTR.
One utility noted that MF/UF made it possible to meet CT requirements and reduce disinfectant
dosages, putting the utility in a better position to comply with the Stage 1 D/DBP Rule.
                                          95

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Table 15. Summary of General Information for the Utilities Contacted
State
Alaska
Arizona
California
California
Colorado
Florida
Hawaii
Hawaii
Water Type
Reservoir
Lake
Reservoir
NR
Lake
NR
Impounded
Direct Runoff
Impounded
Direct Runoff
Capacity
(MGD)
0.43
3.0
0.144
5.0
30°
1.67
3.1
2.2
System
US Filter
Zenon
Aquasource
US Filter
Pall
Zenon
US Filter
US Filter
Install.
Date
Fall 1999
June 1999
Feb1995
Feb1994
June 2001
Fall 2000
May 1997
May 1997
Process Configuration
MF^ Chloramination
-> Nanofitration ->
Chlorination
Equalization (PAC and
KMn04) -> UF ->
Chlorination
UF -> Chemical
disinfection
Strainer -> MF ->
Chlorination
Coagulation &
Sedimentation (PAC,
KMnO4 & Ferric) -> MF
-> UV -> Chloramination
Softening &
Sedimentation (H2SO4)
-> UF
Pre-sedimentation -> MF
-> Chlorination
Pre-sedimentation -> MF
-> Chlorination
Feed Water Quality
Characteristics
- Turbidity = 4 NTU
- TOG > 30 mg/L
- Giardia & Crypto present
- Central Arizona Project
Water (Colorado River)
-Turbidity = 10 NTU
-Total Coliform = 0.8 MPN
NR
-Turbidity = 11.6 NTU
- TOG = 1.9 mg/L
- Alk = 49 mg/L
-Hard = 53 mg/L
- pH = 8.3
- Turbidity = 2-20 NTU
- Turbidity ~ Low-High
- Alk ~ Low
- Turbidity ~ Low-High
- Alk ~ Low
Decision Driver
- Pretreatment
- Removal of Giardia and
Crypto
- Reduce DBPs
- Space limitations
- Low capital costs
- Current regulatory
compliance
- Appropriate technology for
small system
- Current regulatory
compliance
- CT limitations
- Low manpower required
- Removal of Giardia and
Crypto
NR
- Current regulatory
compliance
- Removal of Giardia and
Crypto
- Current regulatory
compliance
- Removal of Giardia and
Crypto
Log Credits Given
by State
NR
- Giardia'. 3-log
- Giardia'. 3-log
- Viruses: 4-log
- Giardia'. 3-log
- Giardia'. 3-log
- Giardia 2. 5- log
- Giardia and
Crypto: 2.5-log
- Giardia and
Crypto: 2.5-log
Monitoring
Requirements
NR
- Particle Counting
- Particle Counting
(SR)
- Pressure Hold Test
(SR)
-TMP Limit (SR)
- Particle Counting
(SR)
- Particle Counting
- Particle Counting
(FSR)
- Particle Counting
(FSR)
                                                     96

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Table 15. Summary of General Information for the Utilities Contacted (continued)
State
Hawaii
Hawaii
Idaho
Kansas
Michigan
Missouri
New Jersey
New York
Oregon
Pennsylvania
Water Type
Impounded
Direct Runoff
Impounded
Direct Runoff
Mountain
Runoff
River
Lake
Lake
NR
River
River
Reservoir
Capacity
(MGD)
9.9
2.2
1.6
3°
7.0
1.0
0.5
0.14"
0.5°
20'
System
US Filter
US Filter
Koch
Koch
US Filter
Koch
Aquasource
Aquasource
Pall
Pall
Install.
Date
May 1998
May 1998
Jan 1997
Feb 2001
Sept 1997
Jul 1999
1997
1993
Sept 2001
Spring
2001
Process Configuration
Pre-sedimentation -^ MF
-^ Chlorination
Coagulation &
Sedimentation ^ MF ^
Chlorination (ammonia
facilities mothballed)
Rock Filter -> UF ->
Chlorination
Coagulation &
Sedimentation -^UF
Strainer -> MF ->
Chlorination
Pre-sedimentation ->
Lime & Polymer Addition
-> Rapid-rate
Sedimentation ->
Equalization -> UF
Screen -> MF ->
Chlorination
NR
NR
MF -> Chlorination
Feed Water Quality
Characteristics
- Turbidity ~ Low-High
- Alk ~ Low
- Color ~ 180 TCU (High)
-Turbidity = 0.2-0.4 NTU
-Turbidity = 1-5 NTU
- Turbidity = 0.2-6 NTU
- pH = 7.8
- Hard = 45 mg/L
-Turbidity = 0.7-0.9 NTU
- Turbidity < 2 NTU
NR
- TOG < 1 mg/L
- pH 7.0
- Alk =30 mg/L
- Turbidity = 0.02-1 NTU
- pH = 7.6-8.7
- TSS = 0-2 mg/L
- Hard = 78-184 mg/L
Decision Driver
- Current regulatory
compliance
- Removal of Giardia and
Crypto
- Current regulatory
compliance
- Removal of Giardia and
Crypto
- Space limitations
- Future unfiltered
regulations compliance
NR
- Future regulatory
compliance
NR
- Current regulatory
compliance
NR
- Future unfiltered
regulations
NR
Log Credits Given
by State
- Giardia and
Crypto: 2.5-log
- Giardia and
Crypto: 2.5-log
- Giardia and
Crypto: 3-log
- Viruses: 4-log
NR
- Giardia: 3-log
- Viruses: 3.5-log
NR
NR
NR
- Pathogens: 3-log
- Giardia: 4-log
- Viruses: 0-log
Monitoring
Requirements
- Particle Counting
(FSR)
- Particle Counting
(FSR)
- Pressure Hold Test
(SR)
NR
- Particle Counting
(SR)
- Pressure Hold Test
(SR)
- Particle Counting
(FSR)
NR
NR
- Pressure Hold Test
(SR)
- Particle Counting
(SR)
- Pressure Hold Test
(SR)
                                                     97

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Table 15.  Summary of General Information for the Utilities Contacted (continued)
State
Texas
Texas
Utah
Virginia
Washington
Wisconsin
Water Type
River
Lake & River
River
GWUDI
River
NR
Capacity
(MGD)
9.0
7.8
1.2
2.5
6.5
14
System
Aquasource
Pall
US Filter
Koch
US Filter
US Filter
Install.
Date
Jan 2000
Dec 1999
June 1999
Aug 1999
June 2000
Oct 1998
Process Configuration
Ferric sulfate -^Clarifier
-> Pre-filter -> UF
Sedimentation -> MF ->
Chlorination
Pre-sedimentation ->
Pre-filter^ MF^
Chlorination
Pre-filter -> UF ->
Chlorination
Pre-screens -> MF ->
Chlorination -> Caustic
& Fluoride
Strainer -> MF ->
Chlorination -> Fluoride
& Corrosion Inhibitor
Feed Water Quality
Characteristics
- Turbidity ~ High
- Turbidity ~ High
- TOG ~ High
-Turbidity = 5-10 NTU
- TOG = 2 mg/L
- Alk = 230 mg/L
- Hard = 220 mg/L
- Turbidity = 0.5 NTU
- Turbidity < 2 NTU
- TOG < 2 mg/L
- pH = 7.0
- TOG = 2-3 mg/L
- pH = 7.5
- Alk= 100 mg/L
- Hard = 140 mg/L
Decision Driver
- Customer preferences
- HighTHM levels
- Removal of Crypto
- Variable water quality
- Remote location
- Low costs
NR
- Ease of operation
- Future unfiltered
regulations
- Removal of Crypto
- Future regulatory
compliance
Log Credits Given
by State
- Giardia'. 3-log
- Viruses: 2-log
- Giardia and
Crypto'. 3-log
- Viruses: 0-log
- Giardia'. 3-log
- Viruses: 0.5-log
- Giardia'. 2-log
- Giardia and
Crypto. 3-log
- Giardia'. 3-log
Monitoring
Requirements
- Particle Counting
(SR)
- Pressure Hold Test
(SR)
NR
- Pressure Hold Test
(SR)
- Pressure Hold Test
(SR)
- Particle Counting
(SR)
- Pressure Hold Test
(SR)
- Pressure Hold Test
(SR)
- Sonic Test (SR)
1 -Several utilities indicated that they were awarded credits different from the credits that the state indicates that they grant to MF/UF processes.
2 - The monitoring requirements are listed as the utilities reported them.  Some of the requirements may not be state requirements as indicated.
3 - Pilot studies with future capacities listed
4 - Only pilot study completed
NR - Not reported                                        PC -  Process Configuration
TSS - Total Suspended Solids                              GWUDI - Ground Water Under Direct Influence
Alk - Alkalinity (mg/L as CaCCs)                            Crypto- Cryptosporidium
Hard - Hardness (mg/L as CaCCs)                          SWTR - Surface Water Treatment Rule
MPN - Mean Probable Number                             CT -  (Disinfection) Contact Time
TCU - True Color Units                                    DBPs - Disinfection Byproducts
NTU -  Nephelometric Turbidity Units                        SR -  State Requirement
                                                      FSR- Future State Requirement
                                                                                 98

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MF/UF can remove protozoa, specifically  Cryptosporidium and Giardia, to below detection
limits.  UF has been demonstrated to be capable of removing viruses (see Chapter 3), though the
results are variable and dependent upon the exclusion characteristic of the specific membrane.
The  fact  that these technologies  provide a  barrier  to  pathogenic  microorganisms  makes
membrane filtration an attractive treatment alternative to  conventional technologies.   Several
utilities contacted consider membranes to be a barrier capable of providing a long-term solution
to future microbial contaminants of concern.  For example,  the SWTR included standards for
only Giardia  and viruses,  while  the IESWTR  added  Cryptosporidium removal/inactivation
requirements.  Since membrane filtration removes most pathogens  larger than viruses via size
exclusion, this technology represent a barrier to pathogens  that would potentially be considered
under future regulations. It is worth noting that the Unregulated Contaminant Monitoring Rule
will  gather occurrence  data on  eight microorganisms that have the potential to be addressed
under future regulations.

As a stand-alone technology, membrane filtration is easier to operate than conventional treatment
processes,  which require  more  operator knowledge  and are susceptible  to changes in water
quality. A number of utilities, particularly small utilities, cited automation as  a key factor in the
decision-making process.  One utility stated that it did not want to hire additional treatment plant
staff and consequently selected a process that was "as automated as possible."

Membrane filtration requires less land  area than conventional treatment processes and can be
retrofitted to  existing facilities where little  space is available.  Submersible membranes can be
installed in existing filter beds, after removal of the granular media and underdrain; however, this
can be difficult in  some plant configurations.   One utility in Idaho sited its location in a
mountainous  region and  indicated that the  space  requirements for  slow  sand  filters made
membranes a more attractive  treatment option.   Another  utility  in  Utah chose  membrane
treatment  over conventional treatment due to the problems associated with receiving chemical
shipments at the remote location of the plant.   MF/UF  requires little chemical use other than
periodic  cleaning  and  post-membrane disinfection for  virus inactivation  and secondary
disinfection.

Membranes are commonly used as a physical barrier in a multiple-barrier approach to treatment
for microbial  contaminants.  When used in conjunction with chemical disinfection, and other
physical barriers (such  as  conventional  treatment), membranes provide an  additional level  of
public  health protection. Additionally, several utilities applied membrane filtration to reduce the
level of chemical  disinfection required.  One utility in  Pennsylvania  opted to  use membrane
filtration to treat water in an uncovered finished water reservoir rather than cover it to maintain
the aesthetic quality of the open reservoir (States, et al., 2000).

Capital and operating  costs associated with membrane treatment  are becoming increasingly
competitive with conventional technologies.  Total costs for a 1-MGD MF/UF plant with full
backwash treatment (coagulation, sedimentation, dewatering,  and sludge disposal) are estimated
at $1.39 to $2.06  per  1000 gallons  (depending upon the interest rate and average feed water
temperature (EPA, 2000b).  Costs for similar  sized package conventional plants are estimated at
$0.73 to $0.87 per 1000 gallons (EPA, 1999d), and those costs do not include the treatment of
                                          99

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filter backwash solids.  Several of the utilities contacted installed membranes after they failed to
meet  filtration avoidance  criteria.   MF/UF offered an  economically feasible  alternative  to
conventional treatment or media filtration.

A few  utilities  use MF/UF as a pretreatment for NF or RO  in dual  membrane treatment
applications.  NF  and  RO  membranes,  designed  to remove dissolved contaminants,  are
particularly  susceptible to  fouling when  applied  to surface  waters.   MF  and UF  remove
particulate matter, and thus minimize particulate fouling of NF and RO membranes.  MF/UF are
able to remove suspended particles and pathogens, while NF/RO remove selected salts, synthetic
organic chemicals, and DBF precursors.  A utility in  Alaska with source water TOC  as high as
30 mg/L was able to reduce finished water TTHM levels to 10 - 20 |j,g/L through dual membrane
treatment.   This utility uses chloramines prior to NF to  control biological fouling  on the NF
membranes. Following NF, chlorine is added to achieve breakpoint, allowing free chlorine to be
used as the residual disinfectant (Lozier, et al., 1997).  However, ammonia facilities are available
should this utility decide to use chloramines for residual disinfection in the future.

A utility in Texas  installed UF to address public  concern  over  the use of surface water as a
drinking water supply.  The customers  of this utility had historically been served  by ground
water,  and  were apprehensive when a  nearby river was proposed as an  alternate source  to
alleviate some of the burden on the aquifer. The utility determined membrane filtration was best
suited for treating the river water and addressing public concerns.

7.3  Operational Practices

Utility operational practices varied based on the source water quality, process configuration, and
regulatory requirements.   A summary of the utilities'  operational  information is presented  in
Table 16.  Note that utilities in Westminster, Colorado; Astoria, Oregon; New Rochelle, New
York; Parsons, Kansas; and Pittsburgh, Pennsylvania are not included in the table because those
systems are pilot facilities.   This section discusses operational practices reported by the utilities
contacted, including pretreatment, flux and  transmembrane pressure, backwash practices, clean-
in-place (CIP) practices, monitoring and integrity testing, and observed treatment challenges.

7.3.1   Pretreatment

Pretreatment is used by MF/UF facilities for four general reasons: 1) to control  fouling, 2) to
provide additional treatment, 3) to meet manufacturer warranty  requirements, or 4) to meet state
regulatory requirements.  The majority of installations use pretreatment to improve  feed water
quality and reduce fouling; however, it was  not clear what fraction of the utilities contacted do so
as part of a warranty requirement.  States that require pretreatment, generally  do  so  because of
concerns over economic failure of the system that could result from inadequate pretreatment to
control fouling.
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Table 16. Summary of Operating Practices for Utilities Contacted
State
Alaska
Arizona
California
California
Florida
Hawaii
Hawaii
Hawaii
Hawaii
Idaho
Michigan
Missouri
New Jersey
Texas
Water Type
Reservoir
Lake
Reservoir
NR
NR
Runoff
Runoff
Runoff
Runoff
Runoff
Lake
Lake
NR
River
Capacity
(MOD)
0.43
3.0
0.144
5.0
1.67
3.1
2.2
9.9
2.2
1.6
7.0
1.0
0.5
9.0
System
Type
MF
UF
UF
MF
UF
MF
MF
MF
MF
UF
MF
UF
UF
UF
Membrane
Configuration
Ol
Ol
10
Ol
Ol
Ol
Ol
Ol
Ol
10
Ol
IO
IO
IO
TMPMax
(Psi)
15
NR
NR
17
20
NR
NR
NR
NR
NR
17
25
NR
NR
Flux
(9")
NR
38.5
NR
NR
NR
67
88
67
88
NR
20 - 65
(30 Avg)
96
72 (D)
66 (Max)
60
Backwash
Procedures
Every 30 min or
TMPMax
Every 15 min
(30 sec duration)
Time- based
TMPMax -based
Every 15 min
(30 sec duration)
Total of 90 min/day
Total of 90 min/day
Total of 90 min/day
Total of 90 min/day
Every 60 min
Every 60 min
Every 60 min
Every 30-60 min
Time/Temp/Flux/
Turbidity-based
Backwash
Treatment
NR
- Discharged to
WWTF
-Chlorine -^ Unlined
pond
NR
NR
NR
NR
NR
NR
- Settling Tank ->
Infiltration pond
- Discharged to lake
- Discharged to
reservoir
NR
- Evaporative lagoon
Cleaning-in-Place
Procedures
- Every 2-3 weeks at
0.5*QDesign
- Every month with Chlorine
and NaOH
- Every year
NR
- NaOCI, Citric acid, NaOH,
Na2SO4 treatment
NR
NR
NR
NR
- Every month with Chlorine
and NaOH
- Every 6 weeks with
Memclean
- Every 90 days orTMP>15
psi with NaOH and Chlorine
- Every month
- Every 15-20 days with
Citric acid
- Short-term chemical
cleaning schedule
Pressure Hold
Test Frequency
Every 24 hrs
NA
NA
Every 4 hrs
NA
Every 24 hrs
Every 24 hrs
Every 24 hrs
Every 24 hrs
NR
NA
NA
NA
Every 10 days
Treatment Challenges
Poorer WQ during winter
NR
Seasonal WQ variation
Seasonal WQ variation
(after winter storms)
NR
Seasonal WQ variation
Seasonal WQ variation
Seasonal WQ variation
Seasonal WQ variation
Color
Variable WQ, algae,
operator skills
NR
TOG
Iron, microbiological
fouling
Turbidity spikes
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Table 16.  Summary of Operating Practices for Utilities Contacted (continued)
State
Texas
Utah
Virginia
Washington
Wisconsin
Water Type
Lake &
River
River
GWUDI
River
NR
Capacity
(MOD)
7.8
1.2
2.5
6.5
14
System
Type
MF
MF
UF
MF
MF
Membrane
Configuration
Ol
Ol
10
Ol
Ol
TMFW
(Psi)
20
18
25-30
15
NR
Flux
(9")
52
100
101
50-70
NR
Backwash
Procedures
Every 20 min
Every 20 min
(air and raw water)
Every 30-90 min
Every 40 min
Every 40 min
Backwash
Treatment
NR
- Holding pond -^
River
- Discharged to
stream
- Recovery System
Membrane -> WTP
Headworks
-Waste Basin -^
Land application
- Discharged to
WWTF
Cleaning-in-Place
Procedures
- Citric acid and NaOH
treatment
- Every 4-6 weeks (or <100
LMH/bar)with Memclean
and Citric acid
- Chlorine, Citric acid,
Sulfuric acid, NaOH
treatment
- Every month with Citric
acid and NaOH
- Every 6 days at Qoesign
Pressure Hold
Test Frequency
NR
NR
Every 24 hrs
Every 4 hrs
Every 8 hrs
Treatment Challenges
WQ highly variable, TOG
NR
Turbidity spikes following
storms, Fouling
problems
Turbidity spikes following
storms
Turbidity spikes following
storms, Crypto removal
NR - Not reported
NA - Not applicable
D - Design
W - Winter
S - Summer
Ol - Outside-in
IO - Inside-out
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Pretreatment reduces the solids load applied to the membrane, permitting use of a higher flux and
thus reducing the required membrane area. Alternatively, the lower solids loading could allow a
lower transmembrane pressure to  be  applied, which would reduce operating  costs.  Another
benefit of pretreatment is that it  results in longer runtimes between  backwash and cleaning
events.  All of these factors can allow systems to achieve a higher system recovery,  maximizing
water production and lowering overall costs.

Pretreatment is also used to  protect  the membrane from contaminants that  could  damage the
system.   Prefilters are necessary to remove large suspended solids  and some bacteria, and
provide protection against fiber and pore plugging as well as biological fouling and degradation.
Pre-sedimentation,   with  or  without  coagulation,   can  remove  suspended   solids  and
microorganisms, reducing the solids load to the membrane.

Pretreatment may also be applied to remove  contaminants that would otherwise not  be removed
by membrane filtration alone.  Oxidation, coagulation and sedimentation can remove dissolved
contaminants (e.g.,  iron, manganese,  TOC,  etc.) that may otherwise pass through  a MF/UF
membrane.  Coagulation may also  result in agglomeration  of particles and microorganisms that
would normally be too small to be retained by MF/UF membranes.

The utilities contacted can be divided into two categories with respect to pretreatment: those that
use only pre-filtration prior to membrane treatment, and  those that use sedimentation.  Seven of
the utilities  contacted  use only pre-filtration.  Most use strainers, but several use alternate
filtration technologies.  For example, one plant in Idaho also uses a rock filter. Three others use
400 to 500  jam  strainers to remove  larger paniculate matter and debris from the  feed water.
Twelve utilities use sedimentation as pretreatment, and seven of these utilities use coagulation in
conjunction with sedimentation.

It  is  worth noting that  pretreatment chemicals  must be  evaluated for compatibility with
membrane  materials.   For  example,  cationic polymers are  frequently  used  to enhance the
coagulation  and flocculation  processes  in  a  conventional treatment  plant;  however,  most
membranes  are  anionic  in  nature and are incompatible  with these polymers.   Failure  to
completely remove the polymer from the membrane feed water can  result in  substantial fouling
of the membrane.   Another consideration is  the  coagulant  itself.    Most  membranes  are
compatible with ferric salts, but alum has resulted in significant fouling with some membranes.

Two of the  utilities contacted use no additional pretreatment prior to  MF or UF  membranes.
There was no apparent correlation between the source water for these utilities and their decision
to not include additional pretreatment.  The two  remaining  utilities  provided no  information
regarding their treatment practices.

Two other utilities  took advantage of retrofit situations to incorporate pretreatment.  In both
cases, new membrane facilities were installed following  coagulation and sedimentation.  One of
these  plants added UF to expand  treatment plant capacity.  The other replaced conventional
media filtration with UF, but has mothballed the media  filters for emergency use.  Another
retrofit option involves using existing media filter basins to house immersed  membranes.  This
allows utilities to take advantage of existing plant piping and basins with minimal modification.
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7.3.2  Flux and Transmembrane Pressure

The  operating fluxes reported  by these  utilities  ranged from  30 to 100  gfd  and averaged
approximately 75 gfd, varying with manufacturer specifications, membrane configuration and
level of pretreatment.  The average flux for outside-in configurations was approximately 65 gfd
and  ranged from  30  to 100  gfd.   The  average  flux  for  inside-out  configurations  was
approximately 80 gfd and ranged from 60 to 100 gfd.

Maximum  TMP  is  primarily  dependent upon membrane  configuration  and manufacturer
specifications.  The utilities contacted were asked to provide the maximum TMP at which their
system operates.  The maximum TMP ranged  from  15 to 30  psi with an average of 20 psi for all
of the utilities contacted that utilize positive pressure membrane systems.  The average maximum
TMP for outside-in configurations was 17 psi and ranged from 15 to  20   psi.  The average
maximum TMP for inside-out configurations  was 30 psi and ranged from 25 to 35 psi.  Two of
the utilities contacted utilize vacuum pressure  systems, and the maximum  TMP for these systems
was -12 psi.

7.3.3  Backwash Practices

Periodic backwashing is necessary to remove the solids that  accumulate at the membrane surface
during a filtration cycle.   For most systems, backwashing is fully automatic,  and is initiated:  1)
when the TMP reaches a programmed setpoint, 2) after a programmed period of operation,
regardless of the TMP, or 3) after a given volume of filtrate is  produced.  Both liquid and air
backwashing are employed with MF/UF technology.

Of the utilities contacted, 16 initiated backwashing based upon operation time at  a frequency
ranging from 15 to 90 minutes.  One utility based backwashing on a combination of operational
time and TMP, and another  based its decision to backwash solely on TMP.  A new facility in
Texas had a much  more complex approach that considered feed water temperature and turbidity
levels, as well as time and flux.

Six utilities operate in an inside-out mode and use purely hydraulic washes, and  13  utilities
operate in an outside-in configuration and use an air/water combination. Of those 13 utilities, 11
feed air from  the  filtrate side of the  membrane and water on  the feed side only  during the
backwash period.  The remaining two are submerged membrane systems,  and use  continuous
feed side aeration to prevent  solids build-up on the  membrane surface and minimize flux decline
or increasing TMP  during operation.

Backwash  water  will  typically  have  elevated   concentrations   of  suspended  solids  and
microorganisms. Since this may potentially include high concentrations of pathogens, backwash
water must be treated and/or disposed  of in  a proper manner.   The  backwash water from
conventional filtration plants will be  regulated under the proposed Filter Backwash Rule (see
Section 2.1.4); however,  it is unclear at this time whether or not membrane backwash water will
need to comply with the requirements of this rule.
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The utilities contacted were asked to provide information regarding the disposal of backwash
water.  Disposal practices ranged from direct discharge to a receiving body of water to treatment
by additional membranes and recycle to the treatment plant headworks.   The reported  disposal
practices, from most to least frequently cited, are as follows:

   1)  Discharge to a receiving body of water (stream, river,  lake, or pond) other than the raw
       water source with or without additional treatment

   2)  Discharge to sanitary sewer

   3)  Recycle to the head of plant

   4)  Discharge to evaporation pond

   5)  Discharge to raw water source

   6)  Use for irrigation/land application

Five of the utilities contacted  reported that they discharged  MF/UF backwash  to a receiving
body.  Two utilities provide no additional treatment of the backwash and discharge directly to a
nearby stream and lake, respectively.  Two other utilities clarify backwash before discharging to
a nearby river and unlined pond, respectively.   Still another utility chlorinates the backwash
before it is discharged to an unlined pond.

The backwash from two utilities is treated at municipal wastewater treatment facilities.   One of
these  utilities discharges  spent backwash directly to  the sanitary  sewer; the  other  pumps
backwash to the wastewater plant.  Neither utility reported any pretreatment requirements for
their backwash stream.

One utility in Washington treats spent backwash water from eight primary production MF units
with a ninth MF unit. During the first nine months of operation, filtrate from the ninth unit was
recycled to the primary production  raw water line.  Based on  filtrate water quality and  integrity
test data from the  ninth unit, the state now allows discharge of the ninth  unit filtrate to the
clearwell,  along with the filtrate from the  eight  primary production units. Backwash from the
ninth unit is stored  in a  waste basin until it is discharged over  an open field using spray  nozzles.
The waste stream  is not disinfected prior to disposal.   A  second basin captures CIP waste
streams, which are pumped and trucked to the city's wastewater treatment facility.

The use of evaporation  ponds may  be an  option for treatment of spent backwash for utilities in
warm climates.  However,  it may be advantageous to have  an  alternative, such as discharge to a
sanitary sewer, available for emergency situations.  A utility in Texas reported that evaporation
ponds have been sufficient to handle their entire backwash  flow, and after one year of operation
it had not yet had to discharge to the sanitary sewer.

A utility in Missouri discharges spent backwash to the raw water reservoir.  No treatment was
reported prior to discharge to the reservoir.  Contaminant loading was  not a  concern for this
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utility, primarily due to the extensive level of pretreatment, including pre-sedimentation, lime
and polymer addition, and rapid-rate filtration.

Another backwash disposal practice reported by the utilities contacted was land application for
irrigation. Only one utility reported this as its sole method of disposal, although another utilized
a  combination of  recycle flow and land application.   Neither of these utilities  reported
disinfecting backwash prior to land application.

7.3.4  Clean-in-Place Practices

When foulants can no longer be removed from the membrane surface by backwashing, chemical
cleaning is required.  Chemical cleaning of MF/UF  membranes is typically referred to as a clean-
in-place  operation.   The  frequency  with  which CIPs  must be performed is  affected by
pretreatment, feed water quality, mode of operation, manufacturer specifications, nature of the
foulant, and  other  operating parameters.   A CIP may be initiated  based upon a scheduled
cleaning interval, at a specific TMP or flux, or based on a rate of increase in TMP.  CIP practices
can include the use of detergents, acids, bases, oxidizing agents,  chelating agents, and enzymatic
cleaners.

The CIP frequency varied from once every two weeks to once per year for the utilities contacted.
The most common practice was to perform CIPs  at least once per month as part of  standard
operating practices. Eight utilities perform CIPs as part of a routine operating schedule. Five of
those utilities perform cleaning at least once per month, one performs cleaning every 1000 hours
(i.e., approximately 6 weeks), one is a new facility that expects to clean quarterly, and one cleans
annually.  One of the utilities that cleans at least once per month varies the frequency depending
upon plant production.  At design flow, cleaning is conducted every six days.  However, when
production is at approximately 70 percent of design capacity, the frequency is reduced to every
18 to 22 days.  The utility that cleans annually takes the system  off-line for cleaning and  uses
distribution system storage to satisfy demand during a CIP event.

Four of the utilities contacted initiate cleaning based upon a loss in membrane flux or an increase
in TMP.   The frequency of cleaning  for these utilities ranged from every two to three weeks to
approximately  90  days.   The two remaining utilities  that provided CIP information initiate
cleaning based  on a combination of time and TMP. That is, cleaning is initiated if TMP reaches
a maximum value or if some period of operation time  passes, whichever occurs first.   This
reflects the fact that most plants operate to achieve a constant production to meet demand,  and
the TMP is increased to maintain production as the  membranes foul.

The types of chemicals used for CIP  varied depending  on  the degree of fouling as well as the
membrane manufacturer's requirements. Citric acid followed by sodium hydroxide was the most
frequently reported combination of  chemical cleaners  and was  used by  five of the utilities
contacted.  Two of those utilities also used chlorine for cleaning.  Three utilities soaked their
membranes in a high strength chlorine solution followed by  cleaning with caustic.  Finally,  two
utilities used proprietary surfactants that were recommended by the manufacturer.
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An adequate rinse period (similar to a filter-to-waste cycle in a conventional  granular media
filter) is necessary following a CIP  to ensure the removal  of residual  cleaning agents.  Spent
cleaning solution may be acidic or basic in nature, contain high levels of free chlorine, or contain
other constituents of concern.  As a result, proper disposal of cleaning solutions is necessary.
The most common  disposal method for spent cleaning solution was neutralization followed by
discharge to a sanitary sewer or receiving  body (i.e., river, stream, or lake). One utility reported
that it collected spent cleaning solution and delivered it to the wastewater treatment facility by
truck.  Another utility neutralized spent cleaning solution and then  pumped it to an evaporation
pond.

7.3.5  Monitoring and Integrity Testing

In addition to the turbidity requirements of the SWTR, there were a number of integrity testing
and monitoring requirements imposed by the state regulatory agencies as discussed in Chapter 6.
These ranged from continuous monitoring methods,  such as particle counting, to periodic direct
integrity tests.

Only two of the utilities contacted conducted monitoring in excess  of that required by the  state
regulatory agency.  Both are conducting  particle counting as a method of ensuring membrane
integrity.   When continuous  monitoring  was  conducted, either voluntarily or to meet  state
requirements, particle counting was the method employed by all of the utilities contacted. Other
methods are available, such as laser turbidimetry, but none were used by  the utilities contacted.

No utility reported conducting direct integrity testing in excess of that required by the state.  Of
the nine required to  conduct direct integrity testing, all  nine used the pressure  hold test.  The
frequency of the test varied by utility from once every four hours to once every ten days.

The data collected indicate  that very few of the utilities and state agencies  have implemented
monitoring  programs  or regulatory requirements  that link  integrity monitoring to  risk of
microbial passage.  For example, in  many states there are no integrity monitoring requirements
beyond  turbidity monitoring which lacks the sensitivity to detect small breaches that could pose a
significant risk of microbial passage.

Particle counting methods are more sensitive than turbidity monitoring for detecting breaches in
membrane integrity,  although, these methods are not without limitations. Using particle counters
on  combined effluent (i.e., filtrate from a  number of different skids) may not provide sufficient
sensitivity to detect small breaches of concern, and  this  difficulty increases with the number of
skids to which a particle counter is  applied.  A breach  in integrity can be masked by dilution
when the filtrate from several skids is combined.
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7.3.6  Treatment Challenges

The  most commonly reported  treatment challenge was variable raw water quality.   Utilities
frequently noted  increases in raw water turbidity following rain or winter storm  events, a
phenomenon characteristic of many surface water supplies.  While many utilities cited the ability
of membrane filtration to handle variations in feed water quality as a significant influence  for
selecting the technology, the high solids load associated with these events accelerates fouling and
increases the frequency at which systems must be backwashed or cleaned.

The  second  most common challenge reported was  algae growth  and microbial  fouling of the
membranes.  Most of the utilities contacted were able to use chlorinated water for backwashing,
or use chlorine as part of the CIP process, and eliminate biological activity on the membrane.
However, this challenge  may be more significant  for utilities that employ membranes that  are
sensitive to chlorine.

Two utilities reported TOC as a treatment challenge.  MF and UF are not capable of removing
TOC without  additional treatment.   However,  significant TOC  reductions can  be  achieved
through  the inclusion of treatment  processes  specifically  designed  for  this purpose (i.e.,
coagulation  and sedimentation,  or PAC).   One  utility reported a 30 percent reduction in raw
water  TOC  through coagulation, sedimentation,  and rapid-rate filtration  as pretreatment to
MF/UF.   This same utility  also has the ability to bring granular activated  carbon (GAC)
contactors on-line following MF/UF  if TOC  reduction is  insufficient through  conventional
treatment. To date, this utility has not had to use its GAC contactors.

One  utility experienced problems with iron fouling early in  the technology demonstration phase.
Adding chlorine to the backwash water oxidized the iron and  reduced the effect of fouling.
However, they  still experience some problems during cold  weather, and as a result the plant is
taken off-line during winter months.

Other issues raised include equipment problems  and operator training.  One utility noted it had
difficulty with its vacuum pumps, another cited recurring fiber breakage.  These are issues that
can be resolved by improved equipment specifications and improved quality control during the
manufacturing process.  Finally, one utility reported operator skill level as a challenge.  Many
utilities install  MF/UF  technology because it  is  almost entirely automated.   However, this
particular utility was once an unfiltered source, and thus did not have significant experience with
the operation of water treatment processes.  As a result, operator skill was a very real  challenge
at this utility.   The membrane supplier in this  case  provided  extensive  operator training to
eliminate this barrier.

7.4   Summary

A utility may  choose to  install membranes for a variety of reasons.  In the majority  cases the
decision  was influenced by current or future regulatory requirements.  However, concern over
microbial contaminants, independent of the regulations, is also frequently cited as a reason  for
selecting membrane  filtration.  In addition,  membrane filtration systems are easier to operate,
less susceptible to changes in source water quality,  and require fewer operators than conventional
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treatment plants.  As membrane filtration becomes more cost-competitive, its use continues to
grow, and membranes are being used in  an increasingly proactive manner to improve drinking
water quality and comply with new drinking water regulations.

Pretreatment is used for four general reasons:  1) to reduce the foulant load applied  to  the
membrane, 2) to provide additional treatment, 3) to meet manufacturer warranty requirements, or
4) to meet state regulatory requirements.  There was no apparent correlation between raw water
quality and the level of pretreatment applied by  the utilities contacted.  Pretreatment was most
commonly used to improve membrane feed water quality and reduce fouling, resulting in longer
run times between  backwashing  and CIP events.  Reducing the solids load can also lower the
TMP requirements resulting in lower operating costs.  In addition to solids removal, pretreatment
processes  such  as  coagulation  and  sedimentation  have  the  ability  to  remove  dissolved
contaminants that may otherwise pass through MF/UF.  Regulatory  requirements to implement
pretreatment are often based on a concern regarding economic failure of membrane system due
to excessive fouling and cleaning requirements.

Manufacturer  specifications and membrane  system  configuration are two  critical factors in
determining key design and  operational  variables like flux and TMP.   However,  feed water
quality, pretreatment conditions, and  economic considerations will also impact  the  optimal
design and operational parameters for a given application.

Backwash and CIP operations are generally initiated based upon operating time or TMP.  The
interval between membrane backwashes typically ranges from 15 to 90 minutes regardless of the
criteria used to initiate backwash, while  CIP frequency ranges  from once every two weeks to
once per year.  Backwashing is a physical scouring of the membrane that generally uses water or
a combination of  air and water; however, some plants employ chlorine during backwash to
control biological  fouling.  A CIP is a  more involved  cleaning procedure  in which  chemical
agents, such as acids, bases, oxidants or  surfactants,  are used to remove foulants that are  not
typically removed during a backwash event.

Monitoring  and integrity testing requirements  vary by  state and  can include  continuous
monitoring and/or periodic direct integrity testing. The majority  of the utilities contacted did not
conduct monitoring or testing beyond the  state requirements; however, a few utilities do conduct
discretionary indirect monitoring.  When direct integrity testing was conducted, the pressure hold
test was most  commonly used.   Some utilities supplemented the pressure hold test with sonic
testing or the bubble point test to pinpoint breaches in integrity.

The most commonly reported treatment challenge facing the utilities contacted is dealing  with
fouling events  caused by water quality fluctuations.  However, most utilities did not feel this was
a major concern and generally noted that  one of the benefits of membrane filtration is its ability
to handle influent water quality fluctuations.  Microbial fouling  was frequently reported,  but
easily remedied through backwashing with chlorinated water or chemical cleaning.  Dissolved
contaminants, such as iron, may be the most difficult foulants  to address, although the use of
oxidants has been used to control iron fouling with some success.  Pretreatment by coagulation
and sedimentation may also be used to reduce fouling caused by some dissolved contaminants.
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Generally, the utilities contacted reported few operational issues with their membrane systems.
Most agreed that membranes provided higher quality finished water and required less operator
skill than conventional treatment.  In addition, MF/UF offered these utilities  a competitively
priced, long-term solution for compliance with existing and future regulatory requirements.
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8.0   SUMMARY AND CONCLUSIONS
One of the greatest health risk management challenges facing drinking water suppliers today is
the control of microbial contaminants, such as bacteria, viruses and protozoa (e.g., Giardia and
Cryptosporidiuni).   This point is emphasized by recent drinking  water regulations  that have
focused on the control of waterborne pathogens.  The SWTR mandates filtration for all surface
water systems that do not meet filtration avoidance criteria, requires minimum levels of removal
and/or inactivation  for viruses (4-1 og) and Giardia (3-log),  and  set a turbidity standard  for
combined filter  effluent.    The  IESWTR establishes  more  stringent  filtered  water quality
standards for turbidity and sets a MCLG of zero for Cryptosporidium  for large systems utilizing
filtration.  The LTIESWTR extends the requirements of the IESWTR to small systems.  Most
recently, the LT2ESWTR  agreement in principle proposes to use  influent  Cryptosporidium
concentrations to determine any additional treatment requirements for this organism.

MF and UF  are low-pressure membrane filtration technologies that  have  gained considerable
acceptance in the  drinking water industry over the past ten years.   Both have  consistently
demonstrated the ability to  remove suspended paniculate matter, including many  regulated and
unregulated pathogens.  These processes can be used effectively to meet the turbidity standards
and disinfection/removal requirements of the various  surface water treatment rules.

Membrane filtration systems are relatively easy to operate,  less susceptible  to changes in source
water quality, and require fewer operators than conventional treatment plants. Utilities contacted
during this project pointed out that  membranes  provided higher quality  finished water and
required less  operator skill  than conventional treatment.  As membrane filtration becomes more
cost-competitive, it  is applied  more frequently in a  proactive manner to maintain and improve
drinking water quality rather than in  a reactive manner simply to comply with  new drinking
water regulations.

The decision to install membrane filtration is primarily  influenced by existing and anticipated
regulatory requirements, with secondary considerations given to site specific issues such as  space
constraints,  manpower  issues, and  chemical use.    Concern over microbial  contaminants,
independent of the regulations, is also frequently cited as a reason for selecting membranes.  A
thorough examination of available literature indicates that MF and  UF processes can greatly
reduce protozoan cyst and  bacteria concentrations,  often to detection limits.  In addition, UF
processes have demonstrated the ability to remove viruses to detection limits in many cases.

The predominant removal mechanism  for protozoan  cysts and bacteria is sieving,  since the pore
size of most membranes is typically at least an order of magnitude smaller than the size of these
organisms. A number of membrane challenge studies reported Giardia removals ranging from
4- to 7.3-log, and Cryptosporidium removals ranging from 4.2- to  greater than 8-log.  In nearly
every study,  Giardia and  Cryptosporidium  were  removed to below detection  limits, and
variations  in reported log removals were a function of feed concentration.

Unlike protozoa removal, virus removal is impacted  by factors other than the pore size, such as
membrane surface charge, solution pH, and cake layer formation. This is due to the small size of
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viruses, which are smaller in size than all MF, and some UF, membrane pore sizes.  Reported
virus removals ranged from 0- to 7.9-log.

Although MF and UF represent a physical barrier to particles and organisms that are larger than
the exclusion characteristic of the membrane, a breach in integrity resulting from a broken  or
damaged fiber or seal can compromise this barrier.  The risk of microbial passage due to a breach
in integrity  results in a  need for a  reliable, routine method of verifying membrane integrity.
There are a number of direct and indirect methods that provide a practical means of verifying the
integrity of a  membrane system; however,  there  is a range in sensitivity among  the  various
methods.

Direct methods are non-destructive techniques that are applied to  the physical  elements of the
membrane  module and  system components  to identify and/or  isolate leaks.  The  primary
disadvantage of existing direct methods is that  they cannot be applied continuously while the
membrane filtration system is in operation,  although future  innovations may allow continuous,
on-line direct  integrity testing.  A secondary disadvantage for all direct methods  except the
pressure hold test is the current lack of automation for these tests.  Direct methods also indicate
nothing specific  about filtrate water quality.   However, results  of most direct integrity test
methods can be related to a breach of a specific size, which can be correlated to a certain level of
contamination.   The four most commonly applied direct monitoring methods are the pressure
hold test, diffusive air flow test, bubble point test, and sonic sensing analysis.

The pressure hold and diffusive air flow tests are typically applied to a rack of modules, allowing
a rapid assessment of integrity over a large number of fibers.  Furthermore,  these methods are
very  sensitive, and  can detect a small number  of  broken  fibers over a  rack  of modules.
Depending on the manner in which these tests are applied, they can verify integrity at a level that
would achieve greater than 5-log removal of Cryptosporidium.  Based upon the manner in which
these  tests have been applied in the past, the diffusive air  flow test has demonstrated  greater
sensitivity to ensure removal greater than 5-log.  However, limits on  the pressure that  can be
applied during these tests will determine the smallest hole that will produce a response during the
test.  Manufacturers  typically  specify that  pressure  hold tests be conducted  in the range  of
approximately  15 to 20 psi, which corresponds to a  hole size of approximately 0.5  |j,m.
Similarly, a vacuum hold test is limited to a test pressure of -15  psi, which corresponds to a
minimum detectable breach size of approximately 0.5 |j,m.  Testing at these levels will produce a
response from holes smaller  than protozoan cysts and many bacteria, but would not produce a
response from  a hole the size of even the largest virus (~ 0.1 |j,m).

Indirect methods are  not applied to the membrane module, but rather monitor some aspect  of
filtrate water quality as a surrogate measure of integrity.  These methods typically  monitor for
deviations in filtrate water quality relative to an established baseline to provide an indication of a
potential integrity problem.  While the indirect methods have the disadvantage of only being able
to suggest potential integrity problems, there are some benefits to using these methods. First, the
most common methods of indirect testing operate in a continuous, on-line mode.  In addition, the
same  indirect  methods  and  testing instruments  can be applied  to  any membrane  system,
independent of manufacturer,  system  configuration,  or any  other  parameter intrinsic to  a
proprietary system.  However, there are some potential  implementation issues associated with
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particle counting and air  entrainment in  systems that  utilize  air backwashes or air scour to
minimize fouling of the  membrane  surface.   The three  most  commonly  applied  indirect
monitoring methods are particle counting, particle monitoring, and turbidity monitoring.

Indirect methods can be valuable integrity testing tools  if sufficiently sensitive.  The sensitivity
of an indirect method as an integrity monitoring tool  is dependent upon its  ability to detect
fluctuations in filtrate quality relative to a baseline established for an integral system. A breach
in integrity will result in increased particle concentrations; however, the contribution  of particles
from a breach will be diluted by filtrate from intact fibers.  This dilution effect will  mask small
breaches unless  indirect methods are sufficiently sensitive to detect the resulting infinitesimal
change in filtrate quality.  The impact of this dilution effect on method sensitivity is a function of
the flow and particle concentration from the breach relative to the flow and particle concentration
from intact fibers.

Of the three commonly used indirect methods, particle counters are the most sensitive, followed
by particle monitors  and then turbidimeters.  Although the sensitivity of these methods will vary
from site to site,  in general it  is acknowledged that current indirect methods lack the sensitivity
necessary to detect small breaches over  a rack of modules that could compromise  removal at
levels of concern. However, indirect methods can complement direct integrity testing since they
provide some level of continuous assurance against catastrophic failure between direct integrity
test events.

In regulating membrane filtration technologies,  state agencies have  had to consider the  factors
previously  discussed  related  to  process performance, removal  efficiencies,  and integrity
monitoring techniques.  Current federal surface water treatment regulations do not  specifically
address membrane filtration technology; thus the twenty-seven states with operational membrane
filtration plants  have had to  develop an approach  for regulating this technology.  This  has
resulted in variable requirements across the states; however, there are three common  elements of
most state regulatory approaches to membrane filtration: demonstration of treatment efficacy,
determination of removal credits, and monitoring requirements.

Although most states require  some demonstration of treatment efficiency,  there is a range of
approaches to performing this demonstration.  At one extreme, states rely on existing  data and do
not require  further demonstration of product performance.  At the  other end of the spectrum,
some states require  product  certification,  site-specific pilot testing  and  full-scale  process
demonstration.  Pilot testing has been the most common  approach to performance demonstration,
with 90% of the  states contacted during this project requiring pilot testing in some or all cases.
However, as experience is gained with this technology and national certification programs are
developed, some  states have indicated a willingness to relax pilot testing requirements.

Determination of removal credits  is based on a variety of factors  including demonstration of
treatment efficiency, total removal/inactivation  requirements, experience with the  technology,
and approach to multiple  barrier treatment.  The literature contains a vast amount of data from
challenge  studies demonstrating  very high  removals  of  cysts  and  cyst-sized particles  by
membrane filtration,  in many cases to below detection.  However, state primacy agencies do not
award these high removal  credits due to other factors considered when making the determination,
                                          113

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and in many  cases they require a minimum level  of chemical inactivation  regardless of the
demonstrated removal efficacy.  Also, states rarely grant removal credits in excess of the federal
requirements for removal/inactivation of pathogens.

Most of the states contacted during this project grant between 2.5- and 3-log of Giardia removal
credit  for  MF/UF  membranes.    Only  seven  states  have  awarded  removal  credit  for
Cryptosporidium ranging from 2- to 4-log.  In most cases, states granted the same protozoa
removal credits to MF and UF membranes, which is consistent  with the results from challenge
studies that demonstrate removal of protozoa to below detection by both MF and UF processes.
With only a few exceptions, states did not grant virus removal credits to MF processes, and in no
case was  the  virus removal credit greater than 0.5-log.  Seven states awarded virus removal
credit to membranes classified as UF processes, with credits up to the 4-logs required under the
SWTR.  A commonality among the various regulatory approaches is that in almost all cases
some level of chemical disinfection was required for MF/UF filtrate.

There were also significant differences  in the monitoring required by different states.  Fourteen
of the 29  states did not require any integrity monitoring for MF/UF plants aside from turbidity.
Of the remaining 15 states, 12  require physical  integrity testing with or without continuous
monitoring  and  one state  requires only continuous testing.  All  states  that require periodic
physical  integrity testing  stipulate  use of the pressure hold  test,  while states  that require
continuous testing permit use of particle counting,  particle monitoring, laser turbidimetry, or
pressure drop.

The response from commonly used integrity tests  can be related to the level  of contamination,
and thus the microbial risk, resulting from an integrity breach.  This relationship can be used to
demonstrate that even with an integrity breach that is sufficiently  small, membrane filtration
systems have  the  ability  to  achieve  pathogen  removal  above that normally possible  with
conventional treatment processes (Jacangelo, et al., 1997).  However, the philosophy that most
state agencies have adopted with respect  to integrity  monitoring is that any integrity breach
detected must be  immediately addressed,  regardless of the impact of the breach  on removal
efficiency. Few states have considered the sensitivity and detection limit of integrity monitoring
methods in granting removal credits and establishing  monitoring requirements.

Integrity testing is a key component in a membrane filtration application, both from a regulatory
and public health  perspective.  However, both direct and indirect methods have limitations as
integrity testing  tools.  Pressure-driven  tests are extremely sensitive and can verify integrity to
very high levels; however, these methods are not continuous, and provide no measure of filtrate
water quality.  Indirect methods  are continuous and on-line, but cannot verify integrity to the
levels necessary to ensure high removal efficiency.   However, direct and indirect methods can
complement each other in a comprehensive monitoring program. Seven of the states contacted
during this project do require a two tier approach for integrity monitoring:  periodic direct testing
to verify integrity  to the required level, and indirect monitoring  to ensure that a minimum level
of performance is achieved on a continuous basis.

Many of  the differences  in the various approaches  adopted by state agencies are a result of
differences  in the philosophical  approach to drinking  water treatment,  different  levels of
                                          114

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experience with membrane processes, and a lack of formal guidance that adequately addresses
this technology.  These differences present challenges to the implementation of this technology.
However, the development of formal federal guidance regarding pathogen removal by membrane
filtration may go  a  long way  towards standardizing the application and  regulation of this
technology.
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9.0    REFERENCES
Adham, S.S., J.G. Jacangelo, and J-M. Laine, J-M (1995). "Low-Pressure Membranes:
       Assessing Integrity. J. AWWA, 87:3:62.

Allen, M.J., J.L. Clancy, and E.W. Rice (2000). "The Plain, Hard Truth About Pathogen
       Monitoring," J. AWWA, 92:9:64-76.

American Water Works Association (1999). Water Quality and Treatment: A Handbook of
       Community Water Supplies, Fifth Edition, McGraw Hill, New York, NY.

American Water Works Association (2000). "Walkerton Boil Notice Lifted as Inquiry Reveals
       Falsified Reports," WaterWeek, 9:50 (12/18/2000).

Anselme, C. and E. P. Jacobs (1996). "Ultrafiltration," Chapter in Water Treatment Membrane
       Processes, American Water Works Association Research Foundation, Lyonnaise des
       Eaux, Water Research Commission of South Africa, McGraw Hill, New York, NY.

Aptel, P. and C.A. Buckley (1996). "Categories of Membrane Operations," Chapter in Water
       Treatment Membrane Processes, American Water Works Association Research
       Foundation, Lyonnaise des Eaux, Water Research Commission of South Africa, McGraw
       Hill, New York, NY.

Banerjee, A., F. Hanson, E. Paoli, C. Korbe, R. Kolman, D. Nelson, K. Smith, and M.
       Lambertson (1999a). "Ultra Low Range Instrument Increases Turbidimetric Sensitivity
       by Two Orders of Magnitude," AWWA Water Quality Technology Conference
       Proceedings, October 31 -November 4, 1999, Tampa, FL.

Banerjee, A., K. Carlson, and J. Lozier (2000).  "Monitoring Membrane Integrity Using Ultra
       High Sensitivity Laser Light," AWWA Water Quality Technology Conference
       Proceedings, November 5-9, 2000, Salt Lake City, UT.

Banerjee, A., M. Lambertson, and K. Carlson (1999b). "Sub-Micron Particles in Drinking Water
       and Their Role in Monitoring the Performance of Filtration Processes," AWWA Water
       Quality Technology Conference Proceedings,  October 31 -November 4, 1999, Tampa,
       FL.

Bruce Barrett & Associates (1992). "Consensus Protocol for Acceptance of Alternative Surface
       Water Filtration Technologies in Small System Applications," Western States
       Workgroup, Final Report.

Cheryan, M. (1998). Ultrafiltration and Microfiltration Handbook.  Technomic Publishing Co.,
       Inc., Lancaster, PA.

Chwirka, J.D., B.M. Thomson, and J.M. Stomp III (2000). "Removing Arsenic from Ground
       Water" J. AWWA, 93:3:79.
                                        117

-------
Clair, D., S. Randtke, P. Adams, and S. Shreve (1997). "Microfiltration of a High-Turbidity
       Surface Water with Post- treatment by Nanofiltration and Reverse Osmosis," AWWA
       Membrane Technology Conference Proceedings, February 23 - 26,  1997, New Orleans,
       LA.

Coffey, B. (1992). Conceptual Design Report for Desert Pumping Plant Domestic Water
       Systems, Metropolitan Water District of Southern California-Water  Quality Division.
       September 1992.

Colvin, C., C. Acker, B. Marinas, and J. Lozier (1999). "Mechanisms Responsible for the
       Passage of Microorganisms through RO and NF Membranes," AWWA Membrane
       Technology Conference Proceedings, February 28 - March 3, 1999, Long Beach, CA.

Colvin, C., R. Brauer, N. DiNatale, and T. Scribner (2001).  "Comparing Laser Turbidimetry
       with Conventional Methods for Monitoring MF and UF Membrane  Integrity."  AWWA
       Membrane Technology Conference Proceedings, March 4-7, 2001, San Antonio, TX.

Cote, P. (2001). Personal communication.

Dwyer, P.L., M.R. Collins, A.B. Margolin, and Hogan (1995). "Assessment of MS2
       Bacteriophage Giardia Cysts Cryplosporidium Oocysts and Organic Carbon Removals
       by Hollow Fiber Ultrafiltration," AWWA Membrane Technology Conference
       Proceedings, Reno NV, pp. 487.

EPA (1989). Drinking Watern; National Primary Drinking Water Regulations; Disinfection;
       Turbidity, Giardia lamblia. Viruses, Legionella, and Heterotrophic Bacteria; Final Rule,
       54 FR 27486, June 29, 1989.

EPA (1990). Guidance Manual for Compliance with the Filtration and  Disinfection
       Requirements for Public Water Systems Using Surface Water Sources, Office of Ground
       Water and Drinking Water.

EPA (1995). ICR Protozoan Method for Detecting Giardia Cysts and Cryptosporidium Oocysts
       in Water by a Fluorescent Antibody Procedure, EPA 814-B-95-003, Office of Water.

EPA (1998a). National Primary Drinking Water Regulations: Disinfection and Disinfection
       Byproducts: Final Rule, 63 FR 69390, December 16, 1998.

EPA (1998b). National Primary Drinking Water Regulations; Interim Enhanced Surface Water
       Treatment Rule: Final Rule, 63 FR 69478, December 16,  1998.

EPA (1999a). Microbial and Disinfection Byproduct Rules Simultaneous Compliance Guidance
       Manual, EPA 815-R-99-001, Office of Ground Water and Drinking Water.

EPA (1999b). Method 1622: Cryptosporidium in Water by Filtration/IMS/FA EPA 821-R-99-
       001, Office of Water.
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-------
EPA (1999c). Method 1623: Cryptosporidiwn and Giardia in Water by Filtration/IMS/FA EPA
       821-R-99-006, Office of Water.

EPA (1999d). TechnoloRJes and Costs for the Removal of Arsenic from Drinking Water,
       Prepared by International Consultants, Inc. for the Office of Ground Water and Drinking
       Water under Contract 68-C6-0039.

EPA (2000a). Office of Water, Office of Ground Water and Drinking Water Web Site,
       http ://www. epa. gov/safewater/mdbp/mdbp .html.

EPA (2000b). Technologies and Costs for Control of Microbial Contaminants and Disinfection
       Byproducts, Prepared by Malcolm Pirnie, Inc. for the  Office of Ground Water and
       Drinking Water under Cadmus Group, Inc. Contract 68-C-OO-l 13.

EPA (2000c). National Primary Drinking Water Regulations: Long Term 1 Enhanced Surface
       Water Treatment and Filter Backwash Rule; Proposed Rule, 65 FR  19046, April 10,
       2000.

EPA (2000d). Stage 2 Microbial and Disinfection Byproducts Federal Advisory Committee
       Agreement in Principle; Notice of Agreement in Principle, 65 FR 83015, December 29,
       2000.

EPA (2001). ICR Data Analysis currently in preparation by Office of Ground Water and
       Drinking Water.

Gagliardo, P., S. Adham, and R. Trussel (1997). "Water Repurification Using Reverse Osmosis:
       Thin Film Composite vs. Cellulose Acetate Membranes," AWWA Membrane
       Technology Conference Proceedings, February 23 - 26, 1997, New Orleans, LA.

Gagliardo, P., S. Adham, Y. Chambers, B. Gallagher, M. Sobsey, and R. Trussel (1999).
       "Development of an Innovative Method to Monitor the Integrity of a Membrane Water
       Repurifiation System," AWWA Membrane Technology Conference Proceedings,
       February 28 - March 3, 1999, Long Beach, CA.

Glucina, K., J-M. Laine, and C. Robert (1997). "Integrated Multi-Objective Membrane Systems
       for Surface Water Treatment," AWWA Membrane Technology Conference Proceedings,
       February 23 - 26, 1997, New Orleans, LA.

Glucina, K., J-M Laine, C. Anselme, M. Chamant, and P.  Simonie (1999).  "Acoustic Sensor: A
       Novel Technique for Low Pressure Membrane Integrity Monitoring." AWWA
       Membrane Technology Conference Proceedings, February 28 - March 3, 1999, Long
       Beach, CA.
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Goodrich, J.A., S.Y. Li, and B.W. Lykins, Jr. (1995). "Cost and Performance of Alternative
       Filtration Technologies for Small Communities," AWWA Annual Conference
       Proceedings, 1995.

Hagen, K. (1998). "Removal of Particles, Bacteria, and Parasites with Ultrafiltration for
       Drinking Water Treatment," Desalination, 119:85-91.

Heneghan, K. S., and M.M. Clark (1991). "Surface Water Treatment by Combined Ultra-
       filtration/PAC Adsorption/Coagulation for Removal of Natural Organic, Turbidity, and
       Bacteria," AWWA Membrane Processes Conference Proceedings, Orlando, FL, p. 345.

Hofman,  J.A., M.M. Beumer, E.T. Baars, J.P. van der Hoek and H.M.M. Kopers (1998).
       "Enhanced Surface Water Treatment by Ultrafiltration," Desalination., 119:113-125.

Jacangelo, J.G, M.E. Aeita, K.E.  Cams, E.W. Cummings, and J. Mallevialle (1989). "Assessing
       Hollow-Fiber Ultrafiltration for Particle Removal," J. A WWA,81:11:68.

Jacangelo, J.G, J-M Laine, K.E. Cams, E.W. Cummings and J. Mallevialle (1991). "Low-
       Pressure Membrane Filtration for Removing Giardia and Microbial  Indicators,"
       J.AWWA, 83:9:97.

Jacangelo, J.G., S.S. Adham, and J-M Laine (1995). "Mechanism of Cryptosporidium, Giardia,
       and MS2 Virus Removal by MF and UF," J. AWWA, 87:9:107.

Jacangelo, J.,  S. Adham, and J-M Laine (1997).  Membrane Filtration for Microbial Removal,
       Report No. 90715, American Water Works Association Research Foundation, Denver,
       CO.

Jack, A.M. and M.M. Clark (1998).  "Using PAC-UF to Treat a Low Quality Surface Water,"
       J.AWWA, 90:11:83.

Kachalesky, L.A., and T. Masterson (1995). "Membrane Filtration of Sewage Treatment Plant
       Effluent," AWWA Membrane Technology Conference Proceedings, Reno NV, pp. 517.

Karimi, A.A., J.C. Vickers, and R.F. Harasick (1999).  "Microfiltration goes Hollywood: the Los
       Angeles Experience," J. AWWA, 91:6:90.

Kohl, H.R, D. Smith, D. Bedford, J. Lozier, and B. Fulgham (1993).  "Reclamation of Secondary
       Effluent Using Membrane Filtration," AWWA Membrane Technology Conference
       Proceedings, Baltimore, MD.

Kothari, N., W.A Lovins, C. Robert, S. Chen, K. Kopp, and J.S.  Taylor (1997). "Pilot Scale
       Microfiltration at Manitowoc," AWWA Membrane  Technology  Conference Proceedings,
       New Orleans LA, pp. 173.
                                        120

-------
Kruithof, J.C. P. Hiemstra, P. Kamp, J. van der Hoek, and J.C. Schippers (1999). "Disinfection
       by Integrated Membrane Systems for Water Treatment," AWWA Membrane Technology
       Conference Proceedings, Long Beach, CA.

Kruithof, J.C. P. Hiemstra, P. Kamp, J. van der Hoek, and J.C. Schippers (1997). "Integrated
       Multi-Objective Membrane Systems for Control of Microbials and DBF-Precursors,"
       AWWA Membrane Technology Conference Proceedings, February 23-26, 1997, New
       Orleans, LA.

Landsness, L.B. (2001).  "Accepting MF/UF Technology - Making the Final Cut," AWWA
       Membrane Technology Conference Proceedings, March 4-7, 2001, San Antonio, TX.

Li, S.Y., J.A Goodrich, J.H Owens, G.E. Willeke, F.W. Schaefer, and R.M. Clark (1997).
       "Reliability of Surrogates for Determining Cryptosporidium Removal," J. AWWA.,
       89:5:90.

Lipp, P. and G. Baldauf (2000).  "Enhanced Particle Removal in Drinking Water Treatment
       Plants - Case Studies," Water Sci. Tech.,  41:7:135-142.

Lozier, J.C., G. Jones, and W. Bellamy (1997). "Integrated Membrane Treatment in Alaska,"
       J.AWWA, 89:10:50.

McNamara, T.D., and T.C. Gavin (1997). "Microfiltration Project Case Study, Marquette MI,"
       AWWA Membrane Technology Conference Proceedings, New Orleans, LA, pp. 1097

Melzer, T.H. (1987). Filtration in the Pharmaceutical Industry. Marcel Dekker, Inc., New York.

NSF (2000a). Environmental Technology Verification Report: Physical Removal of
       Cryptosporidium oocysts and Giardia cysts in Drinking Water, Aquasource North
       America, Ultrafiltration System Model A35, Pittsburgh, PA.

NSF (2000b). Environmental Technology Verification Report: Physical Removal of
       Cryptosporidium oocysts and Giardia cysts in Drinking Water, Pall Corporation, WPM-1
       Microfiltration Pilot System, Pittsburgh, PA.

NSF (2000c). Environmental Technology Verification Report: Physical Removal of
       Cryptosporidium oocysts and Giardia cysts in Drinking Water, Leopold Membrane
       Systems, Ultrabar Ultrafiltration System with 60 Inch Mark III Membrane Element,
       Pittsburgh, PA.

NSF (2000d). Environmental Technology Verification Report: Physical Removal of
       Cryptosporidium oocysts and Giardia cysts in Drinking Water, Zenon, ZeeWeed ZW-
       500 Ultrafiltration Membrane System, Pittsburgh, PA.

NSF (2000e). Environmental Technology Verification Report: Physical Removal of
       Microbiological and Particulate Contaminants in Drinking Water, Ionics, UF-1-7T
       Ultrafiltration Membrane System, Escondido, CA.
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NSF (2000f). Environmental Technology Verification Report: Physical Removal of
       Microbiological and Particulate Contaminants in Drinking Water, Zenon, Enhanced
       Coagulation ZeeWeed ZW-500 Ultrafiltration Membrane System, Escondido, CA.

NSF (2000g). Environmental Technology Verification Report: Physical Removal of
       Microbiological and Particulate Contaminants in Drinking Water, Hydranautics,
       Hydracap Ultrafiltration Membrane System, Escondido, CA.

O'Connell J. and S. Danos (1997). "An Innovative Combination of Ozonation and
       Ultrafiltration," AWWA Membrane Technology Conference Proceedings, New Orleans
       LA, pp. 1127.

Oliveri, V.P., G.A. Willinghan, D.Y. Parker,  and J.C. Vickers (1991). "Continuous
       Microfiltration Surface Water," AWWA Membrane Technology Conference
       Proceedings, Orlando, FL.

Oliveri, V.P., G.A. Willinghan, J.C. Vickers, and C. McGahey (1991).  "Continuous
       Microfiltration of Secondary Wastewater Effluent," AWWA Membrane  Technology
       Conference Proceedings, Orlando, FL.

Parker, D.Y., MJ. Leonard, P. Barber, G. Bonic, W. Jones, and K.L. Leavell (1999).
       "Microfiltration Treatment of Filter Backwash Recycle Water from a Drinking Water
       Treatment Facility," AWWA Water Quality Technology Conference Proceedings,
       October 21 - November 3, 1999, Tampa, FL.

Patania, N.L., J.G Jacangelo, L. Cummings,  A. Wilczak, K. Riley, and J. Oppenheimer (1995).
       Optimization of Filtration for Cyst Removal Report No. 90699, American Water Works
       Association Research Foundation, Denver, CO.

Scanlan, P., B. Pohlman, S. Freeman, B. Spillman, and J. Mark (1997). "Membrane Filtration for
       the Removal of Color and TOC from Surface Water," AWWA Membrane Technology
       Conference Proceedings, New Orleans LA, pp. 127.

Schneider, O.D., E. Acs, Leggerio, and S. Nickols  (1999).  "The Use of Microfiltration for
       Backwash Water Treatment," AWWA Annual Conference Proceedings,  June 20 - 24,
       1999, Chicago, IL.

Schulmeyer, P.M. (1995).  Effect of the Cedar River on the Quality of the Ground Water Supply
       for Cedar Rapids, Iowa, US Geological Service, Iowa City, IA.

Seyde, V., D. Clark, E. Akiyoshi, A. Kalinsky, and C. Spangenberg (1999). "Nanofiltration
       Process Microbial Challenge  Studies," AWWA Membrane Technology Conference
       Proceedings, February 28 - March 3,  1999, Long Beach, CA.
                                        122

-------
Spangenberg, C., E. Akiyoshi, A. Kalinsky, V. Seyde, D. Clark and J. Taylor (1999). "Insights
       on Recent Membrane Integrity Testing of an Organic Selective Nanofiltration and Hybrid
       Membrane Arrangement," AWWA Membrane Technology Conference Proceedings,
       February 28 - March 3, 1999, Long Beach, CA.

States, S., M. Scheuring, R. Evans, E. Buzza, B. Movahed, T. Gigliotti, and L. Casson (2000).
       "Membrane Filtration as Posttreatment," J. AWWA, 92:8:59.

Trimboli, P., J. Lozier, and W. Johnson (1999). "Demonstrating the Integrity of a Full-Scale
       Microfiltration Plant Using a Bacillus Spore Challenge Test," AWWA Membrane
       Technology Conference Proceedings, February 28 - March 3, 1999, Long Beach, CA.

Trussel, R, P. Gagliardo, S. Adham, amd A. Olivieri (1998). "Membranes as an Alternate to
       Disinfection," Microfiltration II Conference of the National Water Research Institute
       Proceedings, November 12 - 13, 1998, San Diego, CA.

Van Hoof, S.C.J.M., J.C. Kruithof, and P.C. Kamp (2001). "Development of a New On-Line
       Membrane Integrity Testing System." AWWA Membrane Technology Conference
       Proceedings, March 4 - 7, 2001, San Antonio, TX.

Vickers, J. C, P.E. Johnson and G. Willinghan (1993). "Meeting the Surface Water Treatment
       Rule Using Continuous Microfiltration," AWWA Membrane Technology Conference
       Proceedings, Baltimore, MD, pp. 213.

Valegard, K., L. Liljas, K. Fridborg,  and T. Unge (1990).  "The Three-Dimensional Structure of
       the Bacterial Virus MS2," Nature, 346:36.

Vickers, J.C. (1993). "Aspects of Integrity Testing and Module Construction for Microporous
       Membrane Filters." Unpublished Paper.

Westerhoff, G. and Z.K. Chowdhury (1996).  "Water Treatment Systems," Chapter in Water
       Resources Handbook, L.M. Mays, ed., McGraw Hill, New York, NY.

Willinghan, G.A., J.C. Vickers, and C. McGahey (1993).  "Microfiltration as  Tertiary Treatment
       - Eighteen Month Trial," Proceedings of the AWWA Membrane Technology
       Conference Proceedings, Baltimore, MD.

Yoo, S. R, D. R. Brown, R. J. Pardini, and G.D.  Bentson (1995).  "Microfiltration: A Case
       Study," J.AWWA, 87:3:38.
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                      APPENDIX A

LIST OF FULL-SCALE MF/UF FACILITIES IN THE UNITED STATES
                    (AS OF JUNE 2000)
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Appendix A. List of Full-Scale MF/UF Facilities in the United States (as of June 2000)
State
AK
AK
AK
AK
AK
AK
AK
AK
AZ
AZ
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
Owner
Barrow Utilities and Electric
Coop, Inc
Barrow Utilities and Electric
Coop, Inc
Barrow Utilities and Electric
Coop, Inc
No. Slope Borough
No. Slope Borough
No. Slope Borough
No. Slope Borough
No. Slope Borough
ChollaWTP
Desert Hills
Olivehain Municipal Water
District
East Bay MUD
California Department of
Parks -
Van Damme State Park
City of Santa Cruz
San Jose Water Company
US Forest Service
Cherry Hill/Hetch-Hetchy
Imperial School District
City
Barrow
Barrow
Barrow
Wainwright
Point Hope
Nuiqsut
Point Lay
Atqasuk
Glendale


Valley Springs
Mendocino
Felton
Saratoga
Barton Flats
Mocassin
Imperial
Metropolitan Water District - Intake WTP
Metropolitan Water District - Iron WTP
Metropolitan Water District - Gene WTP
Metropolitan Water District - Hinds WTP
Metropolitan Water District - Eagle WTP
El Dorado Irrigation District -
Strawberry WTP
Allegheny County Water
District
Butano Canyon Water
Company -
Cathedral Grove WTP
Inverness Public Utility
District -
Third Valley WTP
Pacific Gas and Electric -
Tiger Creek WTP
Bolinas Community Public
Utility District
Inverness Public Utility
District -
First Valley WTP
Lompico County Water
District
California Department of
Parks -
Portola State Park
Cucamonga County Water
District
Applegate Water System
Place rville
Nevada City
Pescadero
Inverness
Amador
Bolinas
Inverness
Felton
La Honda
Rancho
Cucamonga
Applegate
Capacity
(mgd)
0.06
0.06
0.36
0.35
0.35
0.35
0.12
0.12
0.85
1
25
0.05
0.026
0.019
3.6
0.01
0.026
0.019
0.019
0.04
0.04
0.019
0.019
0.132
0.04
0.03
0.03
0.03
0.16
0.12
0.06
0.03
4
0.08
Manufacturer
Memcor
Memcor
Memcor
Pall
Pall
Pall
Pall
Pall
Aquasource
Zenon
Zenon
Aquasource
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Installation
Year2
1995
1998
1999
1999
1999
2000
2000
2000
1998
1999
2000
1995
1991
1992
1993
1993
1993
1993
1994
1994
1994
1994
1994
1994
1995
1995
1995
1996
1996
1996
1996
1996
1997
1997
                                      127

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Appendix A. List of Full-Scale MF/UF Facilities in the United States (as of June 2000)
            continued
State
CA
CA
CA
CA
CO
CO
CO
CO
CO
CO
CO
CO
CT
CT
FL
HI
HI
HI
HI
HI
HI
HI
ID
ID
ID
ID
KS
KS
MA
MA
MA
Ml
Ml
Ml
Owner
California Department of
Parks -
Van Damme State Park
Lake Canyon Mutual Water
Company
Solano Irrigation District
Santa Monica
Keystone Ski Resort
City of Ft Lupton/Hudson
Pine Brook Water District
Climax Molybdenum
Company
Town of Dillon
Town of Erie
Uppper Eagle Regional
Water Authority
City of Westminister
Mashantucket Pequot Tribe
Foxwoods Casino
Mashantucket Pequot Tribe
Foxwoods Casino
Marco Island
Hawaii Deparment of Public
Safety -
Waiawa Correctional Facility
City of Maui -
Lahaina WTP
County of Maui -
IAO Ditch
Mililani Memorial Park
County of Maui -
KamoleWTP
County of Maui -
OlindaWTP
Honolulu Board of Water
Supply -
NUUANU Lower Aerator
Oden Water District
Mullan
Shoshone Water District
Boise
Parsons
Public Wholesale Water
Supply District #18
Littleton Water Dept
Gardner
Seekonk
Daviess County
Fayette State Park
City of Marquette
City
Modesto
Los Gatos
Vacaville
Santa Monica
Keystone
Ft Lupton
Boulder
Henderson
Dillon
Erie
Vail
Westminister
Ledyard
Ledyard
Marco Island
Oahu
Maui
Maui
Oahu
Maui
Maui
Honolulu
Sand Pointe
Mullan
Wallace
Boise
Parsons
Public
Wholesale
Water Supply
District #18
Littleton
Gardner
Seekonk
Daviess County
Fayette
Marquette
Capacity
(mgd)
0.03
0.03
1.4
0.75
0.06
2.7
0.24
0.06
0.438
4
5
12
1.8
0.9
1.6
0.12
2.7
1.8
0.08
7.2
0.9
2
1.2
0.6
1.6
4
3
2
1.5
3
4.3
0.288
0.03
7
Manufacturer
Memcor
Memcor
Pall

Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Pall
Pall
Memcor
Memcor
Zenon
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Aquasource
Koch
Koch
Koch
Koch
Koch
Koch
Koch
Zenon
Koch
Memcor
Memcor
Installation
Year2
1998
1999
2000
NR
1987
1997
1997
1997
1999
1999
2001
2001
1996
1999
2000
1996
1997
1997
1997
1998
1998
1998
1999
1997
1997
2000
2000
2001
1997
2000
NR
2001
1997
1997
                                      128

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Appendix A. List of Full-Scale MF/UF Facilities in the United States (as of June 2000)
            continued
State
Ml
Ml
Ml
Ml
Ml
MO
NC
NC
NJ
NV
NV
NV
NV
NY
NY
OK
OK
OR
OR
OR
PA
PA
PA
PA
SD
SD
TN
TX
TX
TX
TX
TX
UT
UT
Owner
Mackinac Island
Linwood Metropolitan Water
District
St. Clair County Water
Supply System -
City of Algonac WTP
East China
Caseville
Cass County -
Public Water Supply District
#7
King Mountain Club
Town of West Jefferson
Clyde Potts WTP
Douglas County
Douglas County
U.S. National Park Service -
Echo Bay
U.S. National Park Service -
Overton Beach
New Rochelle
City of White Plains
Hulah, OK-
Water District #20
Noble County
Oregon Parks and
Recreation Department
Oregon Parks and
Recreation Department
Youngs River/ Lewis &
Clark District
Pittsburgh Water & Sewer
Authority

Littlestown Borough
Authority
Newport Borough
Aberdeen Area Indian
Health Service
Lower Brule Sioux Tribe
Lincoln Memorial University
Bexar MET
Canyon Regional Water
Authority
Canyon Regional Water
Authority
San Patricio Municipal WD
Travis County
Castle Valley Special
Service District
Holliday, UT
City
Mackinac Island
Linwood
Algonac
East China
Caseville
Cass County
Highlands
West Jefferson
Southeast
Morris County
Cave Rock
Cave Rock
Lake Mead
Lake Mead
New Rochelle
White Plains
Hulah
Lucien
Beverly Beach
Bullards Beach
Astoria
Pittsburgh

Littlestown
Borough
Newport
Borough
Ft Thompson
Lower Brule
Harrogate
San Antonio
Hays/Caldwell
Lake Dunlop
San Patricio
Austin
Castle Dale
Holliday
Capacity
(mgd)
2
0.216
2
2.7
1.5
1
0.03
0.12
0.5
0.96
0.16
0.259
0.259
0.09
1.6
0.08
0.12
0.1
0.1
0.5
20
0.36
0.36
0.18
0.5
0.96
0.3
9
1
4
7.8
2
1.2
2.5
Manufacturer
Memcor
Memcor
Memcor
Zenon
Memcor
Koch
Memcor
Memcor
Aquasource
Memcor
Memcor
Memcor
Memcor
Aquasource
Memcor
Koch
Memcor
Pall
Pall
Pall
Pall
Zenon
Zenon
Zenon
Memcor
Memcor
Koch
Aquasource
Koch
Koch
Pall
Pall
Memcor
Pall
Installation
Year2
1998
1999
1999
2000
NR
1999
1998
1998
1997
1997
1997
1999
1999
1993
1999
1999
1997
1999
1999
2000
2000
2000
2000
NR
1999
1999
1995
1999
2000
2001
1999
2000
1999
1999
                                      129

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Appendix A. List of Full-Scale MF/UF Facilities in the United States (as of June 2000) -
            continued
State
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
VA
WA
WA
Wl
Wl
Wl
WY
Owner
Washington County
Services Authority
Nelson County Public Utility
District -
SchuylerWTP
Tomsbrook
Flying J Travel Pizza
Augusta County Service
Authority -
Coles Run WTP
Town of Rural Retreat
Botetourt County -
Vista Corp Park WTP
Edinburg
Town of New Market
Bedford County Public
Service Authority
Giles County Public Service
Authority
Town of Dayton
City of Aberdeen
City of South Bend
Appleton
City of Kenosha
Manitowoc Public Utilities
Meeteetse, WY
City
Chilhowie
Schuyler
Tomsbrook
Clear Brook
Verona
Rural Retreat
Fincastle
Edinburg
New Market
Bedford
Pembroke
Dayton
Aberdeen
South Bend
Appleton
Kenosha
Manitowoc
Meeteetse
Capacity
(mgd)
2.5
0.08
0.12
0.06
0.96
0.42
0.06
0.18
1
0.06
2
2.2
7.11
0.84
24
14
11
0.6
Manufacturer
Koch
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Memcor
Koch
Memcor
Memcor
Pall
Installation
Year2
1999
1994
1997
1997
1998
1998
1998
1998
1998
1998
1999
1999
1999
2000
2001
1998
1999
2000

1. This list includes only MF/UF installations that are subject to the requirements of the SWTR. It does not include
ground water or other applications (such as industrial processes) which are not subject to the provisions of the
SWTR. It is based upon information provided by the manufacturers and is believed to be complete and accurate
however, the information provided was not verified and discrepancies may exist.
2. The year of installation was provided by the manufacturers. In some cases this is the project start date, in others
it may be the plant start-up date, and in others it may only be an approximation.
                                      130

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