United States
     Environmental Protection
     Agency
        RESEARCH PROJECT
National Risk Management Research Laboratoi
       Water Supply and Water Resources Division
        Treatment Technology Evaluation Branch
CHLORAMINATED DRINKING WATER DISTRIBUTION SYSTEM NITRIFICATION: BATCH
AND BlOFILM INACTIVATION STUDIES, MODEL NITRIFYING BlOFILM INVESTIGATIONS,
AND EVALUATION OF OPERATIONAL RESPONSES TO NITRIFICATION EPISODES
                                                             IMPACT STATEMENT
                                              The purpose of this research is for the  U.S. Environmental
                                              Protection Agency (EPA) to address knowledge  gaps in our
                                              understanding of nitrification  in drinking  water distribution
                                              systems. Through increased understanding of nitrifying biofilm,
                                              new methods  to  prevent and  control  nitrification  will  be
                                              elucidated, which will support EPA's goal for clean and safe
                                              water to protect public health.
BACKGROUND:
Nitrification in drinking water distribution systems is undesirable and may result in degradation of water quality and
subsequent non-compliance with existing regulations. Thus, nitrification control is a major issue in practice and likely to
become increasingly important as chloramine use increases.  Unfortunately,  our understanding of distribution system
nitrification and its control is incomplete, which has made this a topic of considerable ongoing research. Many proposed
strategies for nitrification control and  nitrification modeling require  knowledge of both  the  in-situ  growth  and
inactivation kinetics of nitrifiers inhabiting the distribution system. Inactivation kinetics are only available for suspended
nitrifier cultures, but it is well established that suspended cultures are less resistant to disinfectants than biofilm cultures
present in distribution systems. The determination of both the inactivation and degradation kinetics  of ammonia
oxidizing bacteria (AOB) that are likely present in chloraminated drinking water represents a significant knowledge gap
in our understanding of nitrification episodes.

DESCRIPTION:
Studies are currently underway to help fill knowledge gaps that  exist in the general understanding  of nitrification
episodes.  One  of  these gaps  includes  the  need  for growth and  inactivation  kinetic parameters for  nitrifiers
representative of those inhabiting distribution systems to be used in modeling nitrification processes. In order to fill this
gap, new molecular genetics techniques are being used to study both the growth and inactivation kinetics of  pure and
mixed culture nitrifiers.
Another major gap in our understanding of nitrification events is the relative contribution  from suspended culture
nitrifiers compared with nitrifiers growing in biofilm. Nitrifying biofilm research is ongoing with new microelectrodes
capable of probing the full depth of a model distribution system biofilm, determining the profile of the relevant water
quality parameters and enabling calculations of the relative contribution of biofilm nitrification. For development and
      National Risk Management Research Laboratory
      Water Supply and Water Resources Division

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application of the microelectrodes, EPA's National Risk Management Research Laboratory researchers are collaborating
with The University of Cincinnati to develop, validate, and utilize a total chlorine microelectrode to measure disinfectant
profiles within a nitrifying biofilm. In addition to the microelectrode investigations, biofilm annular reactors enriched for
AOB biofilm growth are being used to assess the  temporal changes to nitrifying biofilm community structure after
receiving periodic increases in chloramines. The results of these annular reactor experiments may help elucidate which
AOB species are most resistant to chloramines. In the future, current operational responses to nitrification episodes will
be evaluated with respect to their effect on the biofilm.
EPA GOAL: Goal #2 - Clean & Safe Water; Objective 2.1.1 - Water Safe to Drink
ORD MULTI YEAR PLAN: (DW) Long Term Goal - DW-2 Control, Manage, and Mitigate Health Risks
RESEARCH PARTNERS:
Collaborators: University of Cincinnati
Contractors:  Pegasus Technical Services, Inc.

EXPECTED OUTCOMES AND IMPACTS:
Based on the results of this  research, a better understanding  of the interaction of monochloramine with nitrifiers in
chloraminated distribution system biofilm is anticipated. This  will allow better prevention and  control of nitrification
episodes, which will result in safer drinking water.

OUTPUTS:

   David G. Wahman, Karen A. Wulfeck-Kleier, and Jonathan G. Pressman. Monochloramine Disinfection Kinetics of
    Nitrosomonas europaea by Propidium Monoazide Quantitative PCR and Live/Dead BacLight Methods.  Applied and
    Environmental Microbiology, September 2009, p. 5555-5562, Vol. 75, No. 17
    http://aem.asm.orR/cgi/content/abstract/75/17/5555

   Woo Hyoung Lee, Jonathan G. Pressman, David G. Wahman, Paul L. Bishop, Characterization and application of a
    chlorine microelectrode for measuring monochloramine within a biofilm, Sensors and Actuators B: Chemical, In Press,
    Corrected Proof, Available online 25 January 2010, ISSN 0925-4005, DOI: 10.1016/j.snb.2010.01.025.

RESOURCES:
NRMRL Treatment Technology Evaluation Branch: http://www.epa.gov/ORD/NRMRL/wswrd/tteb.htm
Journal Article:  Monochloramine Disinfection Kinetics of Nitrosomonas europaea by Propidium Monoazide Quantitative
PCR and Live/Dead BacLight Methods, http://aem.asm.org/cgi/content/abstract/75/17/5555

CONTACTS:
Jonathan Pressman, Principal Investigator - (513) 569-7625 orpressman.jonathan@epa.gov
Steven Doub, MediaRelations - (513) 569-7503 ordoub.steven@epa.gov
Michelle Latham, Communications - (513) 569-7601 orlatham.michelle@epa.gov
      National Risk Management Research Laboratory                      www.epa.gov/nrmrl    EPA/600/F-10/009
      Water Supply and Water Resources Division                                               November 2009

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