Maintaining Disinfectant Residual in Distribution … Disinfectant Residual in Distribution Systems...

Maintaining Disinfectant Residual in Distribution Systems

March 11, 2015

PA-AWWA Southeast District & Eastern Section WWOAP

Spring Joint Conference

ObjectivesDistribution System Disinfectant Residuals

• 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

OutlineDistribution System Disinfectant Residuals

• 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

Regulatory Framework - HistoryDistribution System Disinfectant Residuals

• 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)


• 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, and3. Provide a quantifiable minimum target

• Comments on 1987 Draft 1. Many low HPC systems could not meet 0.2 mg/L throughout system2. Increasing chlorine would increase DBPs3. No evidence of any benefit4. 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)


• Summary of Current requirements, based on 1989 SWTR1. Residual – total chlorine, free chlorine, or chlorine dioxide2. Measured at same locations as TCR sites3. Cannot be “undetectable” in >5% of samples each month, for 2

consecutive months4. 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• Presence of disinfectant, regardless of strength, is a useful indicator• Differences in disinfectant efficacy taken into account at Treatment

Plant (primary disinfection)• Major purpose of maintaining residual is to indicate if local contamination

occurring – intrusions into system

Note intrusions can occur in any system, not just Surface Water

Source: Pressman (WQTC 2014)

*Current Requirement

# of States

Detectable Residual

22

Numeric MinimumResidual

28

What are current minimum numeric residual requirements set at?

Source: Ingels (2014) – modified and updatedNote: “*” indicates numeric minimum residual less than 0.2 mg/L; “#” numeric criteria limited to total chlorine

* *

#

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 1

DRAFT State Summary

* *

Source: Daniels (2014), Ingels (2014), Pressman (2014) – modified and updatedNote: “*” indicates numeric minimum residual less than 0.2 mg/L, but unknown

*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 5 (+ 1 proposed)

Minimum Total Chlorine


Source: Daniels (2014), Ingels (2014), Pressman (2014) – modified and updatedNote: “*” indicates numeric minimum residual less than 0.2 mg/L, but unknown

DRAFT State Summary

* *

Regulatory Framework - StateDistribution System Disinfectant Residuals

• Pennsylvania (Current/Pre Revision) – 109.7101. 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

What has changed from Public Health Perspective?Distribution System Disinfectant Residuals

• 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


• CDC, Morbidity and Mortality Weekly Report – September 6, 2013; Surveillance for Waterborne Disease Outbreaks Associated with Drinking Water and Other NonrecreationalWater — 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

• 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, CDCWQTC 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


• 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


• 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


• 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


• 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 cross-

connections 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

Pennsylvania Proposed Pre-Draft Chapter 109 RevisionsDistribution System Disinfectant Residuals

• Technical Advisory Committee for Small Water Systems Meeting, June 18, 2014, Revised Total Coliform Rule

• Other Revisions, Disinfection:


• 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.


• 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

Detectable Residual Operational Strategies/ConsiderationsDistribution System Disinfectant Residuals

• 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


• 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 growth2. Will not reduce risk of waterborne disease in case pathogens

penetrate system3. Will not be effective indicator of intrusion or localized event


• 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

Final Thoughts & Next StepsDistribution System Disinfectant Residuals

• 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

Final Thoughts & Next StepsDistribution System Disinfectant Residuals

• 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

AcknowledgementsDistribution System Disinfectant Residuals

• 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

Maintaining Disinfectant Residual in Distribution … Disinfectant Residual in Distribution Systems...

Documents

Transcript of Maintaining Disinfectant Residual in Distribution … Disinfectant Residual in Distribution Systems...