Treatment Techniques for Controlling Trihalomethanes in Drinking Water


United States
Environmental Protection
Agency
Office of
Research and Development
Washington, DC 20460
EPA/600/2-81/156
September 1981
Treatment
Techniques for
Controlling
Trihatomethanes in
Drinking Water

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                                     EPA/600/2-81/156
                                     September 1981
          TREATMENT TECHNIQUES
 FOR CONTROLLING TRIHALOMETHANES
             IN DRINKING WATER
                          by

JAMES M. SYMONS, ALAN A. STEVENS, ROBERT M. CLARK,
      EDWIN E. GELDREICH, O. THOMAS LOVE, JR.,
                 AND JACK DeMARCO
                    Major Contributors

         J.K. Carswell, W.A. Feige, J.C. Hoff, K.L. Kropp,
       M.M. Lilly, G.S. Logsdon, B.W. Lykins, Jr., R.J. Miltner,
                 L.A. Moore, and B.L. Smith
        DRINKING WATER RESEARCH DIVISION
 MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
       OFFICE OF RESEARCH AND DEVELOPMENT
      U.S. ENVIRONMENTAL PROTECTION AGENCY
                CINCINNATI, OHIO 45268


                               U& Printed on Recycled Paper

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                                PREFACE

   In this volume, the authors attempt to bring together information developed over
the past 6 years on all aspects of trihalomethanes as they relate to drinking water.
The major sections are:

     I.        Introduction
     II.       Measurement
     III.       Mechanism of Formation
     IV.       Measurement for Treatment Evaluation
     V.       Examples of Treatment Evaluation Techniques
     VI.       Treatment Techniques to Remove Trihalomethanes
     VII.      Treatment Techniques to Remove Trihalomethane Precursors
     VIII.     Use of Alternative Disinfectants
     IX.       Maintaining Bacteriologic Quality
     X.       Treatment Costs
     XI.       Summary of Treatment Considerations
     XII.      References
     XIII.     Appendix

  Section I summarizes with references to the primary literature the discovery of the
trihalomethane problem,  health and regulatory information.  Sections II-V also
summarize the literature regarding key background information necessary for an
understanding of approaches to initiating control measures and evaluation of their
degree of success. Sections VI—XI attempt to be more complete treatments of their
subjects including some previously unpublished in-house USEPA—Drinking Water
Research Division (DWRD) research results, and selected references to the primary
literature, sufficient to describe the state-of-the-art knowledge of trihalomethane
treatment techniques, bacteriologic considerations and  economic impact of
trihalomethane control strategies.  Although the authors and contributors realize
that research is  continuing on  this subject and,  therefore, new  data will be
forthcoming, sufficient new information  is available at this time to  warrant this
update of the "Interim Treatment Guide for the Control of Chloroform and Other
Trihalomethanes" June 1976 (Unpublished).
  The authors and contributors hope  this compilation of research material will
prove  useful to  those  challenged with  the  responsibility  of reducing the
trihalomethane content of our Nation's drinking water.

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                               ABSTRACT

  In   1974,  trihalomethanes  (chloroform,   bromodichloromethane,
dibromochloromethane, and bromoform) were discovered to be formed during the
disinfection  step of drinking water if free chlorine was the disinfectant. Various
surveys have shown that this reaction occurs wherever theabove conditions are met.
This, coupled  with the perceived hazard to the consumer's health, led the U.S.
Environmental Protection Agency to amend the National Interim Primary Drinking
Water  Regulations to include a maximum contaminant level of 0,10 mg/ L for total
trihalomethanes. The Safe Drinking Water Act (Public Law 93-523) requires that
every drinking water regulation contain a statement as to what treatment techniques
water utilities can employ to achieve compliance with the regulation as well as the
maximum  contaminant level.  This report satisfies  the treatment document
requirement for the trihalomethane regulation.
  Following a general discussion of measurement  techniques, mechanisms of
formation, and techniques for evaluating treatment,  the three approaches for
controlling trihalomethanes (removing trihalomethanes, removing trihalomethane
precursors, and the use of disinfectants other than free chlorine) are discussed in
detail.  Finally, a thorough discussion of the impact of  trihalomethane control on
bacteriologic quality of drinking water and the cost of the various unit processes
investigated is contained herein.
  For  trihalomethane  removal,  aeration—either  by  diffused-air  or  with
towers—and adsorption—either  by powdered activated carbon or  granular
activated carbon—is effective. The major  disadvantage of this approach is that
trihalomethane precursors  are not removed by  aeration. For trihalomethane
precursor control, effective processes are: 1) oxidation by ozone or chlorine dioxide;
2) clarification by coagulation, settling and filtration,  precipitative softening, or
direct  filtration; or 3) adsorption by  powdered  activated carbon or granular
activated  carbon.  In  addition,  some  modest  removal  or destruction  of
trihalomethane precursors can  be achieved  by  oxidation  with  potassium
permanganate, lowering the pH, or moving the point of chlorination to the clarified
water.  Further, the utility's source should be examined to  determine whether or not it
can  be  improved to  contain  less  trihalomethane  precursor.  Lowering  of
trihalomethane precursor concentrations has the additional advantage of reducing
overall disinfectant demand, thereby reducing the possibility of the formation of all
disinfection byproducts.
  Neither chlorine dioxide, nor ozone, nor chloramines produce trihalomethanes at
significant concentrations when used alone as disinfectants. Furthermore, the cost of
any of these unit processes is very low. The major disadvantage of using alternate
disinfectants for trihalomethane control relates to the lack of any precursor removal.
Although no trihalomethanes will be produced as disinfection byproducts, other
byproducts  will still be produced as the oxidants (disinfectants) react with organic
matter in the water.  Further, some of these byproducts will be halogenated if
chlorine  dioxide  or  chloramines  are used  as the disinfectant  alternative.
Additionally,  each of the disinfectants itself has  inherent  disadvantages; for
example, ozone does not produce a residual for the distribution systgm; chloramine
is a weaker  disinfectant than free chlorine and may itself have unique toxicologic
properties, and chlorine dioxide produces  chlorite and chlorate as inorganic by-
products, anionic species whose health effect is currently unknown.

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  Each of these approaches has advantages and disadvantages as well as different
degrees of effectiveness and unit costs, and these are detailed herein to help water
utility managers, consulting engineers, Primacy Agencies, and others to choose the
best approach  to solve a given problem. Studies have shown that  any of these
techniques,  if  used  properly  and if final disinfection is applied diligently and
monitored closely, can be used for trihalomethane control without any deterioration
in bacteriologic quality at the consumer's tap.
vlii

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                             CONTENTS

Foreword	    iii
Abstract	,	,	,	    vii
Acknowledgments	    xi
   I.   Introduction	     1
   II.   Measurement	     6
  111.   Mechanism of Formation	    10
  IV.   Measurement for Treatment Evaluation	    23
   V.   Examples of Treatment Evaluation Techniques	    29
  VI.   Treatment Techniques to Remove Trihalomethanes (InstTHM)...    36
 VII.   Treatment Techniques to Remove Trihalomethane Precursors
        (THMFP)	    87
VIII.   Use of Alternative Disinfectants	   160
  IX.   Maintaining Bacteriologic Quality 	   194
   X.   Treatment Costs			   228
  XI.   Summary of Treatment Considerations	,	   256
 XII.   References	   26?
XIII.   Appendix	   282
Index	   286

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                       ACKNOWLEDGMENTS
  No project this  large could  be  accomplished alone,  and the authors and
contributors acknowledge the participation of their associates. First, we wish to
thank Gordon G. Robeck,  Director, Drinking Water Research Division, without
whose leadership and management skills the USEPA research reported herein could
not have been conducted. Second, we would like to thank those"other DWRD staff
members who contributed  considerable time  and effort to this work; Diane
Hinderberger, Paul Keller,  Steven Canter, Raymond  Taylor, Martin  J. Allen,
Elizabeth Creamer, Virginia Maphet,  Patricia Pierson, William Winters, Paul
Dorsey, Walter  Elbert, Ronald Dressman, Dennis Seeger, and Clois Slocum.
Thanks is given to Dr. Irwin J. Kugelman of the  Wastewater Research  Division,
Municipal Environmental Research Laboratory, USEPA, who generously gave of
his time to help with the Aeration part of Section VI.
  We wish to acknowledge the contributions of the principal investigators on the
DWRD-sponsored  extramural  projects from  which  much of  the  research
information was collected:
  Mr.  Noel V. Brodtman, Jefferson Parish Water Works, Jefferson  Parish, LA
  Mr.  Patrick R. Cairo, Philadelphia  Water Department, Philadelphia, PA
  Dr. Russell F. Christman, University of North  Carolina, Chapel Hill, NC
  Dr. James K, Edzwald, Clarkson College, Potsdam,  NY
  Dr. Richard S. Engelbrecht, University of Illinois, Urbana-Champaign, IL
  Dr. William H. Glaze, North Texas State University, Demon,  TX
  Dr. Leland L, Harms and Dr, Robert Looyenga, South Dakota School of
     Mines and  Technology, Rapid City, SD
  Mr.  Wendell  R. Inhoffer and Mr.  Richard E.  Roby, Passaic Valley Water
     Commission, Little Falls, NJ
  Dr. Riley Kinman, University of Cincinnati, Cincinnati, OH
  Mr.  David Kittredge, Manchester Waterworks, Manchester, NH
  Mr.  Donald B. Mills, City of Evansville, IN
  Mr.  Richard J.  Miltner, Ohio River Valley  Water Sanitation Commission,
     Cincinnati, OH
  Dr. John.T, O'Conner, University of Missouri, Columbia, MO
  Dr. Charles Oulman, Iowa State University, Ames, IA
  Dr. Aaron  A. Rosen (deceased) and  Mr.  David Hartman, Cincinnati
     Water Works, Cincinnati, OH
  Mr.  Dominick D. Ruggiero, NKRE, P.C., New York, NY
  Dr. Pasquale V. Scarpino, University of Cincinnati, Cincinnati, OH
  Dr. Michael J. Semmens, University of Minnesota, Minneapolis, MN
  Dr. Gordon Sharp, University of North Carolina, Chapel Hill, NC
  Dr. Vernon L, Snoeyink, University of Illinois, Urbana-Champaign, IL
  Dr. Charles A. Sorber, University of Texas, San Antonio, TX
  Dr. Otis Sproul, Ohio State University, Columbus, OH
  Mr.  G. Joseph Sullivan,  Sewage and Water Board of New Orleans,
     New Orleans, LA
  Mr.  Albert Sylvia, Lawrence Experiment Station, Lawrence, MA
  Mr.  Michael Taras,  AWWA Research Foundation, Denver, CO
  Mr.  Paul R. Wood, Florida International University, Miami, FL
  We wish to thank Edward Kispert and  George Hicks of the Cincinnati Water
Works for their assistance and cooperation in supplying water for the in-house

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USEP A-D WR D studies, and we wish to thank those whose time and talent made the
final  publication  of this  volume  possible, particularly,  Marion  Curry,  Ann
Hamilton, and WAPORA, Inc., who handled the final production.
  Finally, we wish  to  thank those who  provided  us with review and helpful
comments: Joseph Cotruvo, Chieh Wu, Craig Vogt, and Stig Regli of the Office of
Drinking Water, USEPA,  Washington, D.C.; Mac Weaver, USEPA Region VI,
Dallas, TX; and David Kittredgeofthe Manchester Water Works, Manchester, NH.
Special thanks are given to our designated peer-reviewers: Dr. Michael J. McGuire
of the Metropolitan  Water District of Southern California, LaVerne, CA,  Dr.
Michael C. Kavanaugh of James M. Montgomery Consulting  Engineers,  Inc.,
Pasadena, CA; and the many staff members of their respective organizations. The
time spent and the depth of their  two reviews, particularly because they involved
their colleagues, were extraordinary and contributed greatly to the accuracy and
final quality of this document.
xi!

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SECTION I
INTRODUCTION

Since the 1974 discovery of trihalomethane formation in drinking water as a result
of chlorinatiori,1'2* much research has been conducted to determine:

1. whether trihalomethanes affect the health of consumers;
1. how trihalomethanes should be measured;
3. how water quality conditions influence trihalomethane formation;
4. treatment techniques) a drinking water utility could use to reduce tri-
halomethane concentrations in distributed water;
5. what effect altering treatment procedures to control trihalomethanes will
have on the bacteriologic quality of distributed water; and
6. the cost of the various treatment possibilities.

The results of these studies "were the basis for the U.S. Environmental Protection
Agency's (USEPA) amendment to the National Interim Primary Drinking Water
Regulations issued November 29, 1979—an amendment establishing a maximum
contaminant level (MCL) of 0.10 mg/L total trihalomethanes (TTHM) in drinking
water.3
Section 1401 (1)(D) of the Safe Drinking Water Act, Public Law 93-523, states
that "the term 'primary drinking water regulation' means a regulation which
contains criteria and procedures to assure a supply of drinking water which
dependably complies with such maximum contaminant levels.. ."and Section 1412
(a)(2) states that "National interim primary drinking water regulations promulgated
under paragraph (a)(l) shall protect health to the extent feasible, using technology,
treatment techniques, and other means, which the Administrator determines are
generally available (taking costs into consideration). . ." Thus, for any regulated
contaminant, a "Treatment Techniques" document must accompany the
establishment of a "Maximum Contaminant LeveP'(MCL) to provide compliance
guidance. This research reportt satisfies the treatment document requirement for the
Trihalomethane Regulation and is a companion to the "Manual of Treatment
Techniques for Meeting the Interim Primary Drinking Water Regulations," EPA-
600/8-77-005 (April, 1978).4 For further information on the Regulation,3 the reader
is referred to a document entitled "Trihalomethane Implementation Guidance"5 that
is available from the Office of Drinking Water, USEPA, Washington, D.C.
The purpose of this research report is to review the discovery of the problem; to
summarize the results of research areas 1, 2, 3, 5, and 6 (above) and the
Trihalomethane Regulation3; and to detail the results of the treatment studies, i.e.,
research area 4 (above).
The first five Sections of this report provide background information needed to
understand and interpret the treatment research presented in Sections VI through
VIII, In Section IX are summarized the findings concerning the impact of changing
treatment to control trihalomethane concentrations on the bacteriologic quality in
distributed water. This information will aid in understanding the interrelationship
•Key papers are cited as references; the reader is referred to the literature citations in each of these papers for a more complete
reading list.
fThis work has been synopsized in "* Removing Trihaiornethanes from Drinking Water—An Overview of Treatment Tech-
niques," J.M. Symonj. A, A. Stevens, R.M. Clark, E.E. Geldreich, O.T. Love, Jr., and J. DeMarco. Water Engrg,& Mgmt,,
128 <7j: 50-53, 56, 61-64, July I9gi.

Section I. Introduction 1

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 between disinfection  practices,  trihalomethane concentrations,  and  resulting
 bactcriologic quality. Section X on "Costs" will help the reader choose the most cost-
 effective treatment technique by combining the information in Sections VI through
 VIII on treatment effectiveness with the cost data in Section X. Section XI is a
 summary of treatment approaches with discussions of cost/effectiveness  tradeoffs
 and examples of hypothetical situations that demonstrate how to select cost-effective
 treatment strategies  for THM  control.

 Discovery

  Although  sporadic  reports  of  the presence  of  chloroform  and   other
 trihalomethanes in finished drinking water occurred before 1974,* the reports that
 year by  Rook1 in The  Netherlands and by Bellar,  Lichtenberg, and  Kroner2 of
 USEPA clearly demonstrated that these contaminants were formed during the water
 treatment process as a result of chlorination. This finding prompted a survey in early
 1975 of 80 water utilities in the United States,  79 of which practiced free residual
 chlorination or combined residual chlorination. This survey, the National Organics
 Reconnaissance Survey (NORS), showed that all of the water utilities that  used free
 chlorine (sometimes  called  chlorine)  in their treatment practice had varying
 concentrations of at least four trihalomethanes in their finished drinking water and
 that they were formed  during treatment.7 Follow-up studies* in 1975 and  1976,
 including the National Organics  Monitoring Survey (NOMS), unpublished  at this
 writing, confirmed this finding with samples collected at 113 locations during three
 different seasons.
  These surveys, combined with like results from all over the world, showed that the
 reaction of chlorine to produce trihalomethanes was widespread and surely  had been
 occurring for  as long as chlorine  had  been  in  use in  water  treatment.
 Trihalomethanes in drinking water had usually escaped detection until 1974 because,
 before that time, the analytic  techniques used to measure the organic content of
 water did not detect them. Once discovered, however, extensive research was begun
 to determine if their presence in drinking water was a health hazard for consumers.
 The results of the health effects studies that led up to the promulgation of the Tri-
 halomethane Regulation' are summarized below.

Health Effects

  People are exposed to chloroform in the air they breathe and the food they eat.
Analysis of the relative contribution of chloroform in drinking water, air, and food
assumes various levels of exposure based on monitoring studies. Drinking water may
contribute from zero to more than 90 percent of the total daily body intake.
  Chloroform has been shown to be rapidly absorbed on oral and intraperitoneal
administration and to be subsequently metabolized to carbon dioxide, chloride ion,
phosgene, and other unidentified metabolites. The metabolic profile of chloroform
in animal species such as mice, rats, and  monkeys is qualitatively similar to that in
humans.
  Mammalian responses to chloroform  exposure include: central nervous system
depression, hepatoxicity, nephrotoxicity, teratogenicity, and carcinogenicity. These
responses are discernible in mammals after oral and inhalation exposures to high
levels of chloroform ranging from 30 to 350 mg/kg of body weight, the intensity of
 response being dependent upon  the dose. Although less toxicologic information
is available for the bromine-containing trihalomethanes, mutagenicjty and carcin-
 ogenicity have been detected in some test systems. Physiological activity is thought
to  be  greater for the bromine-containing trihalomethanes  than  for chloro-
form.
  Although short-term toxic responses to trihalomethanes in drinking water are not
documented, the potential effects of chronic exposures to trihalomethanes should be
a matter of concern. Prolonged administration of chloroform at relatively high dose

 2  Treatment Techniques for Controlling  Trihalomethanes in Drinking Water

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levels,, 1QO to 133 ing/kg,.to rats and mice manifested oncogenic effects, Oncogenic
effects were not observed at the lowest dose levels, 17 mg/kg, in three experiments.
Because  methods do not now  exist to  establish a  "threshold no effect" level of
exposure to carcinogens, the preceding data do not imply that a "safe" level of
exposure can be established for humans.
   Human epidemiologic evidence is inconclusive, although several studies have
found positive associations with some cancer sites. Eighteen retrospective studies,
discussed in detail  in  Attachment 7 of the Trihalomethane Regulation,3 have
investigated some aspect of a relationship between cancer mortality or morbidity
and drinking water variables. Because of various limitations in the epidemiologic
methods, difficulties with the water quality data, and problems with the individual
studies, the present evidence does  not lead to a firm conclusion that an association
exists between contaminants in drinking water and cancer mortality or morbidity;
causal relationships  cannot be  proven on the basis of results from epidemiologic
studies.  When  viewed collectively, however, the epidemiologic studies provide
sufficient evidence for maintaining the hypothesis that a health risk may be occurring
and that the positive relationships may be reflecting a causal association between
constituents of drinking water and cancer mortality.
   Using  different models, the Science Advisory Board, the National Academy of
Sciences, and  USEPA's  Carcinogen   Assessment Group  have  estimated the
incremental risks associated with the'exposure from chloroform in drinking water.
The  exposure, to chloroform from air and food  has  not been included ia these
computations. The risk estimates associated  with theTTHM MCLofO.10 mg/ Lare
essentially the same from the National Academy of Sciences and the Carcinogen
Assessment  Group  computations, i.e., they would predict an  incremental risk of
three to four per 10,000 population consuming 2 liters of water containing 0.10 mg/ L
chloroform  daily for 70 years.
   In summary,"on the basis of the available toxicologic data, chloroform has been
shown to be a carcinogen in mice and rats at high dose levels.  Because its metabolic
pattern in animals is qualitatively  similar to that in humans, chloroform should be
suspected of being a human carcinogen. Epidemiologic studies also suggest a human
risk.  Although documentation of  other trihalomethane  toxicity is  not so well
established, they should be suspected of posing similar risk. Because of  these
suspected health effects, the  Trihalomethane  Regulation was  promulgated  on
November 29, 1979,! The Trihalomethane Regulation is summarized below.

Regulation

History—
   Four statements in the Federal Register**'-*' trace the regulatory history of the
control  of organic contaminants  in drinking water. The first statement was  an
Advance Notice for  Proposed Rulemaking published July 14, 1976, in which the
USEPA  .proposed  several  options for the control of trihalomethanes  and other
organic contaminants in  drinking water and requested comments from the  public.
   As a  result of this statement and the public comments,  USEPA proposed a
two-part Regulation for organic contaminant control in drinking water on February
9, 1978.'° This document specified an MCL for the control of trihalomethanes and
specified that a treatment technique, granular activated carbon, be installed-at water
utilities where source waters were significantly contaminated for thecontrol of other
synthetic organic contaminants.*
   On July 6, 1978, the USEPA published supplemental technical information  on
this subject and extended the public comment period.11 The final Regulation for the
control of trihalomethanes only was published in the Federal Register on November
•Nole, although the February 9.1978, proposed Trihalomethane Regulation10 is often misunderstood 10 say that the USEPA
 was-proposing to r*?i/irplhe use of granular activated carbon adsorption for the control of trihalomethane concentrations.
 this was not the case.   .


                                                     Section I. Introduction  3

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 29, I979.3 In this same document, the proposed regulation of other synthetic organic
 contaminants by using granular activated carbon treatment was deferred, and may
 be re-proposed at a later time.
   On January 11, 1980, the American Water Works Association, together with the
 City  of Englewood, Colorado, and the Capital City Water Company, a Missouri
 corporation, filed a Petition for Review with the U.S. Court of Appeals for the
 District of Columbia Circuit, asking the court for "a review of a final rule" as allowed
 by Section 1448 (a)(l) of the Safe Drinking Water Act (Public Law 93-523). At this
 writing no action has been taken on this Petition.

 Summary of Trlhalomethane Regulation (promulgated November 29,1979)3—
 Maximum Contaminant Level (MCL):
           0.10 mg/L total trihalornethanes (TTHM) (Sum of concentrations of
           compounds 1, 2, 3, and 4,  Table 1).

 Applicability.
           Community water systems that add disinfectant to the treatment process
           (ground and surface).
       Effective:
           Systems >75,OOQ:    2 years after promulgation
           Systems 10-75,000:  4 years after promulgation
           Systems < 10,000:   Discretion of Primacy Agency (State, or USEP A
                                  if  the State does not have primacy)

 Monitoring Requirements:
           Twelve-month-running average of  a minimum of 4 samples per quarter
           per treatment plant taken on the same day. Systems using multiple wells
           drawing raw water from a single  aquifer may, with  Primacy Agency
           approval, be considered to have one treatment plant for determining the
           required number of samples.
       Effective:
           Systems > 75,000:   1 year after  promulgation
           Systems 10-75,000:  3 years after promulgation
           Systems < 10,000:   Primacy Agency discretion
       Sample Locations:
           25 percent at extremity of the distribution system; 75 percent at locations
           representative of the population distribution.

 Adjustment of Sampling Frequency,
           For groundwater systems, reduced monitoring may be appropriate for
           certain systems. The Primacy Agency may reduce the requirements
           through consideration of appropriate data including demonstration by
           the system that the maximum total trihalomethanepotential* (MTP) is
           less than 0.10 mg/ L. The minimum frequency would be one sample'per
           year for MTP taken at the extremity of the distribution system. For
           groundwater systems not meeting the above MTP limit and for surface
           water systems, the Primacy Agency may reduce the monitoring require-
           ments if, after 1 year of data collection, TTHM concentrations are
           consistently below 0.10 mg/L. The minimum frequency  would be one
           sample per quarter per treatment plant for total trihalornethanes taken
          at the extremity of the distribution system. The original frequency would
          be reinstated if the TTHM  concentrations exceed 0.10 mg/L or if the
          treatment or source is modified.
•The maximum total irihalomethane potential is defined as the total trihEtlomethane concentration in a sample after storage
 for ?dt?*at 25*C(?7*F) of above in the presence of a t/istttfeciam residual or after the use of USEPA method 501.1 if no
 diiinfeuarit residual is present after initial storage.


 4  Treatment Techniques for Controlling Trihalornethanes in Drinking Water

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Reporting Requirements:
      To Primacy State:
          Average of each quarterly analysis, within 30 days. Until Primacy States
          have  adopted the regulations,  reporting will  be to USEPA unless
          Primacy State requests receipt of data.
      To Public and Primacy State:             '
          Running-12-month average of each quarterly sample if total trihalo-
          methane concentration  exceeds MCL, as prescribed by the public
          notification  provisions.

Other Requirements:
      To Ensure Microbiologic Quality:    '       '
          Primacy Agency approval of significant modifications in the treatment
          process for the purpose of meeting the TTHM  MCL.
      Analytic Requirements:
          In accordance with specified methods  (purge and trap or liquid-liquid
          extraction) conducted by certified laboratories (see Section II, Measure-
          ment).

  As a further aid to understanding the Regulation3 the reader is referred to the
document "Trihalomethane  Implementation Guidance"* that is available from
Office of Drinking Water, USEPA, Washington, D.C, The Appendix contains the
entire Trihalomethane Regulation from the Federal Register,
                                                    Section I. Introduction  5

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                              SECTION II
                           MEASUREMENT

  Appendix C of the Trihalomethane Regulation3 contains a detailed description of
the USEPA approved methods for sampling and analyzing drinking water for
trihalomethane concentrations. These techniques are summarized here so that the
reader will understand the general approach.

Sample of Collection and Handling

   1. The sample containers should have a total volume of at least 25 mL. Narrow-
mouth screw cap bottles with poiytetrafluoroethylene (PTFE) faced silicon septa cap
liners are strongly recommended.
  2. If the trihalomethane concentration at the time of sampling is desired, a
chemical reducing agent, sodium thiosulfate or sodium sulfite, must be added to the
sample to arrest the  formation of trihalomethanes after sample collection.  If
chemical stabilization is employed, the reagent must be also added to the blanks,
  3. The sample bottles are filled in such a manner that no air bubbles pass through
the sample as the  bottle is filled. The  sample is then inverted; the absence of
entrapped air indicates a successful seal.
  4. If a chemical reducing agent has been added to the sample bottle, the bottle is
shaken vigorously for  1 minute after sealing the bottle.
  5. Blanks are prepared in duplicate at the laboratory by filling and sealing sample
bottles with waters containing a low concentration of organics just before shipping
the sample bottles to the sampling site.  The blanks  are shipped to and from the
sampling site along with the sample bottles. The blanks and the samples collected at a
given site are stored together.
  6. The procedure recommends that all samples be analyzed within  14 days of
collection.

Measurement Techniques

  Although other techniques were investigated,12 the USEPA has approved two gas
chromatographic (GC) techniques for the measurement of trihalomethanes. These
are generally called the "Purge  and  Trap" and  "Liquid-Liquid  Extraction"
techniques. Although  both methods have advantages and disadvantages, when
performed properly, they  have been shown to produce equivalent  results for
trihalomethane analysis.  The two appoved  methods are summarized below:

Purge and Trap Summary—
   1. Trihalomethanes are purged by an inert gas that is bubbled through the aqueous
sample. The trihalomethanes, along with other organic constituents that exhibit low
water solubility and a vapor pressure significantly greater than water, are efficiently
transferred from the aqueous phase to the gaseous phase. These compounds are
swept from the purging device and are trapped-in a short column containing a
suitable sorbent. After a predetermined time, the trapped components are thermally
desorbed and  back flushed onto a gas chromatographic column and separated under
temperature programmed conditions. Measurement is accomplished with a halide
specific detector such as electrolytic conductivity or microcoulometric titration.

6  Treatment  Techniques for Controlling Trihalomathanes in Drinking Water

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   2. Confirmations of identity may be obtained using dissimilar columns, or by mass
 spectrometry (MS).
   3, Aqueous standards, blanks, and unknowns are purged and analyzed under
 identical conditions to compensate for varying purging recoveries.
   4. The total analysis time, assuming  the absence  of other organohalides,  is
 approximately 35 minutes per sample.
 Liquid-Liquid Extraction Summary—
   1. Ten mL of sample are extracted at one time with 2 mL of solvent (pentane,
 hexane, or methylcyclohexane). Three /jL of the extract are then injected into a gas
 chromatograph equipped with a linearized electron capture detector for separation
 and analysis. The absence of trihalomethane peaks in the raw water is generally
 ample evidence of an interference-free finished water analysis.
   2. When needed, confirmatory evidence may be obtained using dissimilar columns
 and temperature programming. When  component concentrations are sufficiently
 high (>50 ^g/ L), halide specific detectors may be employed for improved specificity.
 Unequivocal confirmations of identity  at high concentrations (>50 pg/L) can be
 obtained using MS in place of the electron capture detector. At concentrations below
 50 figi L, unequivocal confirmation of identifications can only be performed by the
 purge and  trap technique  outlined above.
   3. Standards are dosed into water with a low concentration of organics, and the
 standards  are extracted and analyzed  in a manner identical to the samples to
 compensate for possible extraction losses.
   4. The extraction and analysis time  is  10 to 50 minutes per sample depending upon
 the chromatographic conditions chosen.


 Units of Concentration—
   Because the gas chromatographic techniques used to measure trihalomethanes are
 based  on  gravimetric (weighed) standards,  and  because  the Trihalomethane
 Regulation  is based on total trihalomethanes summed on a weight basis, ^tg/L,
 trihalomethane concentrations are most  often seen in the literature expressed in this
 manner.  Frequently, however, expressing the concentration in terms of chemical
 equivalents (mieromoles/ L)  is  more  desirable.  Chemical  equivalents  .are an
 expression  of the number  of molecules present (6.02 X I0"//umol), and are, there-
 fore, a better unit of expression when concentrations of reactive sites(precursors) or
 active sites (adsorption) are being discussed because the interpretation of research
 results  will  not  be  influenced  by the differing  molecular  weights  of the
 trihalomethanes present in various  mixtures.  Throughout  this document, both
 systems of  units are used. In detailed interpretation of research results, the units of
 /amol/ L are the most appropriate; however, to aid the reader in judging the success of
 a water utility to meet the Trihalomethane Regulation,3 the data are more often
 reported in terms of weight concentration (fig/ L) rather than, or in addition to, the
 more chemically meaningful molecular  concentration
Quality Assurance

  The USEPA has set a requirement that, to be approved, a laboratory must be able
to measure the concentration of the individual trihalomethanes as well as the TTHM
concentration in a quality control sample supplied by USEPA to within ±20 percent
of the "true" value. This determination  must  be made annually., If, after an
investigation of its  procedures,  a  laboratory cannot meet this requirement, it is
allowed to demonstrate its effectiveness on repeat quality  control samples.

                                                  Section II. Measurement  7

-------
Surrogate Measurements

Because the analysis for the presence of trihalomethanes is a GC procedure
requiring skilled operators and some time to complete, a simple rapid surrogate
measurement that would predict trihalomethane concentrations seemed desirable.
Because chlorine reacts with precursors to form trihalomethanes, a test that would
measure the precursor concentrations in water was thought to be useful for
predicting trihalomethane concentrations.
No direct test for trihalomethane precursors exists,* so a test for general organic
content was considered as an alternative. The difficulty with using a general organics
test as a measure of trihalomethane precursors is that precursor concentrations are
not a constant percentage of the general organic content. Nevertheless, in the report
of the National Organics Reconnaissance Survey,7 nonpurgeable organic carbonf
(NPOC) was proposed as a surrogate analytic test for the trihalomethane
measurement. The report' suggested that raw water NPOC concentrations could be
used to predict TTHM concentrations in micromoles per liter in finished water (1
/imol/L is approximately 120 fig/L as CHClj).
For the analysis of the data in Reference 7, the NPOC data were grouped in
concentration ranges and the mean TTHM concentration for all data in a given
NPOC range was plotted against the mid-point of the given NPOC range. These data
were very linear when plotted arithmetically. Subsequent research (see Section III,
Mechanism of Formation) showed, however, that several water quality conditions
such as precursor type, temperature, pH, bromide concentration, and disinfectant
type, as well as time of exposure to free chlorine before measurement influenced the
resulting TTHM concentration in a given location. Therefore, the suggestion noted
above was reviewed.
Figure 1, in which all the data from the NORS7 are plotted, shows the scatter
around the line of best fit by least squares. The correlation coefficient, 0.77, is highly
statistically significant, showing that, in general, waters with higher NPOC
concentrations will produce more trihalomethanes than waters with lower NPOC
concentrations. The scatter, however, is great, as demonstrated by the high
calculated 95 percent confidence limit, ±0.5 fimol TTHM per liter (approximately
±60 A
-------
4.0 r
0 5 10 15

SOURCE WATER NPOC CONG, mg/L

Figure 1. Raw water nonpurgeable organic carbon vs. finished
water total trihalomethanes. (Data obtained from the
National Organics Reconnaissance Survey.')
Section If. Measurement 9
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SECTION III
MECHANISM OF FORMATION
Nomenclature
For those readers unfamiliar with organic nomenclature, the following discussion
defines some of the terms. Although methane gas does not seem to be involved, the
reaction of chlorine in water with certain organic compounds, under certain
conditions, produces a group of halogen-substituted single carbon compounds.
These compounds are named as derivatives of methane (CH,i) (Table )).
Under typical circumstances, the trihalomethanes produced in drinking water are
dominated by compounds 1 and 2, but compounds 3 and 4 are frequently found and
compounds 5 and 6 have been detected (Table 1). Note, the arithmetic sum of the
concentrations of compounds 1,2, 3, and 4 has been defined in the Trihalomethane
Regulation3 as "Total Trihalomethanes" (TTHM).

General Mechanism

The formation of trihalomethanes during free chlorination of drinking water
results from a complicated mechanism of attack by aqueous halogen species on
natural aquatic humic substances, i.e., humic and fulvic acids, rather than organic
compounds whose source is industrial water pollution. Thus, trihalomethanes result
from the generalized reaction:

FRF.F PRECURSORS
rwrnRIMP + (HUMIC SUBSTANCES) - TRIHALOMETHANES +
CHLUKIMt AND BROMIDE

Several factors influencing this reaction15"" are summarized below. Design of the
most effective treatment strategy depends on a knowledge of the trihalomethane
formation reaction and the factors controlling it.

Effect of Time

The formation of trihalomethanes under natural conditions is not instantaneous.
Although, under some reaction conditions the formation of trihalomethanes may be
completed in less than an hour, in other circumstances, several days may be required
before the maximum yield of trihalomethanes occurs.
Varying apparent "yields" of trihalomethanes reported throughout the literature
under varying reaction conditions may be influenced by the reaction rate. Thus, a
lower reported "yield" may be the result of the reaction proceeding toward
"completion" at a slower rate. Reaction conditions may also, however, influence the
yield of trihalomethanes obtained at a time when no further reaction appears to be
occurring.
The precise effect on the kinetics (rate) of trihalomethane formation of various
parameters influencing it or yield at "completion" of the reaction is difficult to
predict because of the complexity of the reactions between aqueous free chlorine and
the mixture of precursors of largely unknown structure. Thus, from a practical
standpoint, when yield of trihalomethanes is discussed, the time allowed for the
reaction and other conditions discussed below must be defined.

10 Treatment Techniques for Controlling Trihalomothanes in Drinking Water
-------
TABLE 1, STRUCTURAL FORMULAS AND NAMES
OF THE TRIHALOMETHANES
Formula
Name
Formula
Name
Cl
I
1, H — C — CI
Cl Trichloromethane
(Chloroform)
CHCIj
I
I
6. H - C - Cl
i
Br Bromochloro-
iodomethane
CHCIBrl
Br
I
2. H — C •
I
Cl
Cl

Bromodichloromethane
CHBrCI,
I
I
7. H - C
I
Cl
Chlorodiiodomethane
CHCII,
Br
I '
3. H — C — Cl
Br Dibromochloromethane
CHBrjCI
I
I
8. H - C - Br
I
Br
Dibromoiodo methane
CHBr,I
Br
i
4, H — C — Br
Br Tribromomethane
(Bromoform)
CHBr,
9. H - C — Br
I Bromodiiodomethane
CHBrl,
I
I
6, H — C — Cl
I
Cl
I
10. H - C — I
Dichloroiodomethane
CHCI,I
I Triiodomethane
(lodoform)
CHIa
Section III. Mechanism of Formation 11
-------
Effect of Temperature
When Ohio River water was chlorinated in the laboratory, increasing the
temperature had a positive effect on trihalomethane formation15 (Figure 2). A
corresponding seasonal variation, noticed at a water utility using the same source,
has been shown to be largely a temperature effect. Thus, trihalomethane control
problems become more acute during hot weather when water temperatures are
higher during treatment and distribution.
Data collected by the Ohio River Valley Water Sanitation Commission
(ORSANCO)1* showed that at several water utilities the finished water TTHM
concentrations varied seasonally and were lower in the winter when water
temperatures were lower, although data were not controlled for possible variations
in precursors and other treatment condition variables (Figure 3).
250
200 - -
150 --
X
O)
3.
O
z
O
O
n
O