Maintaining Disinfectant
Residual in Distribution
Systems
PA-AWWA Southeast District
& Eastern Section WWOAP
Spring Joint Conference
March 11, 2015
Distribution System Disinfectant Residuals
Objectives
• Understand current regulatory context for distribution
system disinfectant residuals
– Acknowledge current work of AWWA National Expert
Strategy panel on Distribution Residuals
• Learn what has changed in recent years with regard to
intent and public health risks
• Review relevant PADEP Chapter 109 proposed Pre-draft
revisions
• Start dialogue with other utilities and engage in
appropriate response efforts
Distribution System Disinfectant Residuals
Outline
• Regulatory Framework
– History – Federal & State
– Public health benefits
• What do we know now that we did not know then?
– Public health impact
– Increased knowledge about Distribution System water quality
• Pennsylvania DEP Chapter 109 proposed pre-draft revisions
• Detectable chlorine residual considerations
– Free chlorine
– Chloramine
• Operational Strategies
• Next Steps
Distribution System Disinfectant Residuals
Regulatory Framework - History
• 1975 – National Interim Primary Drinking Water Regulations
“A supplier of water … with the approval of the State … [may] substitute the use of
chlorine residual monitoring for not more than 75 percent of the (coliform) samples
… When the supplier of water exercises the option … he shall maintain no less than
0.2 mg/L free chlorine throughout the public water distribution system …”
• 1987 – Proposed Surface Water Treatment Rule – Subpart H Systems
“Maintain a disinfectant residual in the distribution system (measured as total chlorine,
free chlorine, combined chlorine, or chlorine dioxide) of no less than 0.2 mg/L in
more than 5 percent of the samples each month, for two consecutive months”
• 1989 - Surface Water Treatment Rule
“The residual disinfectant concentration in the distribution system,…cannot be
undetectable in more than 5 percent of the samples each month, for any two
consecutive months that the system serves water to the public. …”
– Source: Pressman (WQTC 2014)
Distribution System Disinfectant Residuals
Regulatory Framework - History
• Intent behind Surface Water Treatment rule residual requirements:
1. Distribution System integrity
- Ensure distribution system is properly maintained & have ability to identify and
limit contamination from outside system
2. Limit growth (regrowth) of HPC and Legionella, and
3. Provide a quantifiable minimum target
• Comments on 1987 Draft
1.
2.
3.
4.
Many low HPC systems could not meet 0.2 mg/L throughout system
Increasing chlorine would increase DBPs
No evidence of any benefit
Requirements should be different for different disinfectants
• EPA revised rule
– require “detectable” in lieu of 0.2 mg/L.
– HPC <500/mL equivalent to detectable residual
Source: Pressman (WQTC 2014)
Distribution System Disinfectant Residuals
Regulatory Framework - History
• Summary of Current requirements, based on 1989 SWTR
1. Residual – total chlorine, free chlorine, or chlorine dioxide
2. Measured at same locations as TCR sites
3. Cannot be “undetectable” in >5% of samples each month, for 2
consecutive months
4. HPC <500/mL considered equivalent to a detectable residual
• EPA Comments on 1989 SWTR
• Disinfectant residuals not a direct measure of performance but an indicator
of system integrity
Note intrusions
can occur in any
• Presence of disinfectant, regardless of strength, is a useful indicator
system, not just
• Differences in disinfectant efficacy taken into account at Treatment
Surface Water
Plant (primary disinfection)
• Major purpose of maintaining residual is to indicate if local contamination
occurring – intrusions into system
Source: Pressman (WQTC 2014)
What are current minimum numeric residual requirements
set at?
DRAFT State Summary
*
* *
#
Current
Requirement
# of
States
Detectable
Residual
22
Numeric Minimum
Residual
28
Source: Ingels (2014) – modified and updated
Note: “*” indicates numeric minimum residual less than
0.2 mg/L; “#” numeric criteria limited to total chlorine
What are current minimum numeric residual
requirements set at?
DRAFT State Summary
*
* *
Minimum Free
Chlorine
Current
Requirement
States
Detectable
20
Unsure of
Numeric criteria
8
0.05 mg/L
1
0.20 mg/L
16
0.3 mg/L
4
(+ 1 proposed)
0.5 mg/L
Source: Daniels (2014), Ingels (2014), Pressman (2014) – modified and updated
Note: “*” indicates numeric minimum residual less than 0.2 mg/L, but unknown
1
What are current minimum numeric residual
requirements set at?
DRAFT State Summary
Minimum Total
Chlorine
*
* *
Current Requirement
States
Detectable
23
Numeric criteria may be
limited to free‐Cl
8
0.05 mg/L
1
0.20 mg/L
5
0.30 mg/L
1
0.50 mg/L
8
0.60 mg/L
1.00 mg/L or higher
Source: Daniels (2014), Ingels (2014), Pressman (2014) – modified and updated
Note: “*” indicates numeric minimum residual less than 0.2 mg/L, but unknown
5 (+ 1
proposed)
Distribution System Disinfectant Residuals
Regulatory Framework - State
• Pennsylvania (Current/Pre Revision) – 109.710
1. Community water systems
•
•
maintain disinfectant residual through DS to ensure compliance with microbiological
MCLs
Monitor same locations as TCR
2. SW/GUDI systems - defines detectable residual as 0.02 mg/l free,
combined, or chlorine dioxide
•
Initiate investigation when can’t be maintained
•
Report # samples < 0.02 mg/L; date time and value for each
•
HPC <500/mL counts as detectable
3. All PWS with MRDL reporting requirements – report monthly average
4. Different than Federal
•
No reporting for meeting 95% ile requirement two months in a row
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• CDC, Morbidity and Mortality Weekly Report – September 6, 2013; Surveillance
for Waterborne Disease Outbreaks Associated with Drinking Water and Other
Nonrecreational Water — United States, 2009–2010
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• CDC, Morbidity and Mortality Weekly Report – September 6, 2013; Surveillance for
Waterborne Disease Outbreaks Associated with Drinking Water and Other Nonrecreational
Water — United States, 2009–2010
• 33 drinking water outbreaks, 1040 illnesses, 9 deaths
• 58% of outbreaks legionella
• Most commonly identified deficiency
– 57.6% legionella in plumbing systems
– 24.2% untreated groundwater
– 12.1% distribution system deficiencies
• Groundwater sources
• Cross connections
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• CDC also recently summarized the following for
Waterborne hospitalizations and deaths
– Enteric pathogens (e.g. e. coli) : lower
– Biofilm pathogens (e.g. legionella): higher
– Classic fecal-oral waterborne disease occurs, but
seldom results in death in US
– Patients infected with biofilm associated disease may
have a more complex clinical picture than GI illnesses
Source: Julie Gargano, CDC
WQTC 2014
Public Health Importance of Premise Plumbing Pathogens
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• Colorado Alamosa
–
–
–
–
2008 Salmonella Outbreak
Up to 1200 illnesses; 1 fatality
Unchlorinated groundwater;
Distribution system deficiency – concrete in ground storage tank with holes
and cracks
• Colorado Proposed Minimum Chlorine Residual Rule – April 2014
– Defines “detectable” as 0.2 mg/L, minimum 0.2 mg/L required for all
systems
• 0.15 mg/L rounds up to 0.2
• 0.14 mg/L rounds down to 0.1 mg/L
– Require 95% of samples in a single month
– Cl2 data paired w/TC – same as now
– Systems should measure chlorine BEFORE collecting TC
• operationally get the chlorine up
– Violation if system cannot meet the level
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• Louisiana – Naegleria fowleri,
– Free living amoeba, ubiquitous in environment, potential high numbers in warm water
– Causes primary amoebic meningoencephalitis (PAM) – rare but lethal
– Found in drinking water in Australia in 1980s
– Recently found in drinking water in Arizona, and cause of two deaths in Louisiana in
2011 and one death in 2013
– Similar to Legionella – exposure pathway is from aerosol, not from drinking
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• Louisiana – Naegleria fowleri
– Found in DeSoto and St. Bernard Parishes,
Louisiana; Testing found amoeba in treated
distribution system water
– Both systems use conventional treatment and chloramine
secondary disinfection to treat surface water
– Common issue in both systems – low to no chlorine
residual; nitrification
– Secondary disinfection critical for N. fowleri control;
Nitrification in chloramine systems poses significant control
challenges
– Readily attach & grow in biofilms
Source: JAWWA,
Bartrand et. al.
October 2014
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• Louisiana – Emergency Distribution Disinfectant Residual Rule
• All points in distribution system need to maintain a disinfectant residual
• Adequate monitoring
– 25% more sites than TCR initially
– By February 2014, 50% more sites
• 0.5 mg/L free chlorine or 0.5 mg/L total chlorine
• Chloramine systems required to develop and submit a Nitrification Control Plan
Source: Causey, et al, 2014 ASDWA Annual Conference
Distribution System Disinfectant Residuals
What has changed from Public Health Perspective?
• Pipe/Distribution system as reactor, not just conveyance of water
What has changed from Public Health Perspective?
– Current Federal regulatory requirements tied to Surface Water or GUDI, but crossconnections and untreated groundwater involved in oubtreaks
– Opportunistic pathogens (non-enteric) – present in soil can contaminate any
distribution system, legionella others too such as Mycobacterium avium (MAC), thrive
in biofilm
– Different exposure pathway – aerosol
– Regrowth in premise plumbing – do we need to consider minimum number at curb
box/meter to mitigate premise plumbing regrowth; nitrification control essential
– Pipe/Distribution system as reactor
Distribution System Disinfectant Residuals
Pennsylvania Proposed Pre-Draft Chapter 109 Revisions
• Technical Advisory Committee for Small Water Systems Meeting, June 18,
2014, Revised Total Coliform Rule
• Other Revisions, Disinfection:
Distribution System Disinfectant Residuals
Pennsylvania Proposed Pre-Draft Chapter 109 Revisions
• Technical Advisory Committee for Small Water Systems Meeting, June 18,
2014, Revised Total Coliform Rule
• Other Revisions, Disinfection
• “Mandate minimum disinfection residual of 0.30 mg/L free chlorine (or
1.00 mg/L total chlorine) throughout distribution system for all CWSs and
any NCWS with 4-log treatment”
• “Failure to maintain minimum disinfectant residual throughout distribution
system for more than 4 hours is a Tier 2 violation”
• Unofficial info from PA - AWWA WUC meeting, that 1.00 mg/L total
chlorine will be changed to 0.50 mg/L for chloraminated systems when
officially published.
Distribution System Disinfectant Residuals
Pennsylvania Proposed Pre-Draft Chapter 109 Revisions
• Same time line as PA implementation of Revised Total Coliform Rule
(RTCR)
• RTCR and other Chapter 109 Revisions including changes to
Disinfection expected to be published April 2015
• Federal RTCR effective April 2016
• PADEP mostly likely will apply for extension
• Unofficially, longer time frame may be allowed for compliance with
disinfectant residual requirements
• Preamble will contain justification and cost benefit analysis
• State will be looking for comments on implementation during “60 day”
public comment period
Distribution System Disinfectant Residuals
Detectable Residual Operational Strategies/Considerations
• No Quick Fix or Silver Bullet
• Years, decades where operationally “trace/detectable” okay
• Reduce water age
• Storage tank management/turnover
-
Seasonal operation
• Flushing –
-
Localized spot flushing for deadends for turnover
Unidirectional or ice pigging for biofilm removal
Water loss considerations – No DES pilot
• Increasing Chlorine at Entry point
- Compliance issues with DBPs;
- Aerators in Tanks may help
• Booster Chlorination
- Establish chlorine booster stations to reduce amount needed to increase at
Entry point
- Chloramine systems – recombine ammonia
Distribution System Disinfectant Residuals
Detectable Residual Operational Strategies/Considerations
• Nitrification Considerations for Chloramine Systems
- Nitrification is a biological process where once it takes hold can
quickly deplete chlorine residuals
- As chlorine decays in system, leaves ammonia as food source
for nitrifying bacteria
- Ammonia oxidizing bacteria and nitrite oxidizing bacteria are
food source for coliforms and support HPC growth
- More bacteria – more chlorine demand and cycle continues….
- Death versus growth
- Per Pressman, WQTC 2014, “detectable is horrible for
nitrification prevention”. Trace total chlorine does not meet
requirements for healthy distribution disinfectant residual
1. Will not limit biological growth
2. Will not reduce risk of waterborne disease in case pathogens
penetrate system
3. Will not be effective indicator of intrusion or localized event
Distribution System Disinfectant Residuals
Detectable Residual Operational Strategies/Considerations
• Chloramine System Strategies
– Understand Chloramine chemistry
- Nitrification Monitoring and Control plan is critical
- Chlorine to Ammonia ratio of 5:1 at Entry/Feed points
- Higher pH promotes higher Chloramine Stability
- Aqua has increased system pH from 7.0-7.2 to 7.5
- Higher Chloramine doses at Entry point
- Aqua has increased from 1.5 to 2.0 mg/L to 3.0 mg/L
- Minimize/eliminate blending with free chlorine – chemical
decomposition of chloramine residual
Distribution System Disinfectant Residuals
Final Thoughts & Next Steps
• Intent behind higher residual requirements something Utilities will
support
• PA needs a dialogue/forum to flesh out details and implementation
• Compliance Time Frame is a critical issue
– Will not be able to go from 0.02 mg/L to higher levels for free and
total overnight (or in four hours)
– DEP assessment that compliance “should not be an issue” faulty –
based on system averages
– May need public outreach strategy – Aqua already has higher
customer complaints on chlorine taste & odor
– Tank Mixers/Booster Stations take planning and time
Distribution System Disinfectant Residuals
Final Thoughts & Next Steps
• Implementation Issues
– Compliance 100% versus 95%ile
– Proposed Tier 2 Violation - Public notification requirements
should not conflict with intent of Federal RTCR
• Call to investigate & fix versus meaningless PN
– Revised sampling plans coordinate with RTCR
• Include deadends; Include downstream of tanks; representative of
pressure zones
– Need to work on more meaningful stakeholder process beyond
the Small System TAC
– In meanwhile, Utilities need to work together, outreach to others
and comment during 60 Day comment period
Distribution System Disinfectant Residuals
Acknowledgements
• AWWA WITAF National Expert Panel on Distribution
System Residuals
–
–
–
–
Jake Causey, Louisiana Dept. of Health and Hospitals
Tyson Ingels, State of Colorado
Steve Via, AWWA
Jonathan Pressman, USEPA Office of Research &
Development
• Mike Pickel & Chuck Hertz, Aqua
March 11, 2015