Effective Microbial Control Strategies for Main Breaks and Depressurization. WaterRF 4307 Webcast May24 24, 2012

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1 Effective Microbial Control Strategies for Main Breaks and Depressurization WaterRF 4307 Webcast May24 24, Water Research Foundation. ALL RIGHTS RESERVED. No part of this presentation may be copied, reproduced, or otherwise utilized without permission. Asset Management UV EDCs Customer Service Climate Change 966 Timeline

2 Project Schedule: WaterRF 4307 Project Start: October 5, 200 Project End: June 5, 203 Project Budget: Cash: $350,000 (= $30,000 (UK DWI) + $320,000 (WaterRF) Third Party Contribution: i $ 33,000 Total: $ 827, Project #: 452 Published: 20 Contractor: American Water The quantitative microbial risk assessment (QMRA) model was developed and was adapted into the current (#4307) project to study microbial infection risks caused by main breaks. 2

3 Webcast Speakers Mark LeChevallier, Ph. D Director, Research & Environmental Stewardship at the American Water Tim Thomure, PMP Arizona Water Group Manager HDR Engineering Q & A Enteryour question Enter your question into the question pane at the lower left hand side of the screen. 3

4 Project Webcast Effective Microbial Control Strategies for Main Breaks and Depressurization Project 4307 Sponsored by Water Research Foundation and the U.K. Drinking Water Inspectorate May 24, 202 in association with with 7 Participating Utilities in association with with 8 4

5 Project Purpose Improve utility responses to main breaks and depressurization events to better protect public health. 9 Project Objectives. Evaluate the effectiveness of disinfection i and operational practices to mitigate risks. 2. Identify parameters to quantify the level of control achieved. 5

6 Scientists & Engineers Practical Guidelines to Reduce Risk Associated with Main Breaks and Depressurization Operators & Practitioners Project Approach STEP Define Terminology and Establish the Baseline of Practice STEP 2 STEP 3 STEP 4 STEP 5 Conduct Laboratory and Pilot Studies and Risk Modeling Identify/Pilot Test Field and Monitoring Activities Develop Tiered Risk Management Strategy Including Multiple Barriers Prepare Work Products and Final Report 6

7 Step Questionnaire Intended to gather data and procedures Questionnaire distributed with follow-up calls when needed Representative sample of industry Basis for selecting Featured Programs What is the rate of main breaks (i.e. # / mile) that are encountered by yyour utility annually? What criteria do you use for release-to-service after repairing a water main break? What is the typical crew size for repairing water main breaks for pipes larger/ smaller than 6-inches diameter? Step : Questionnaire (Cont.) 27 Utilities: Population range from 0, to over 7 million System sizes up to 25,000 miles of pipeline Mix of chlorinated and chloraminated systems Results: Maximum of over.4 main breaks/mile/year Median of 0.8 break/mile/year comparable to prior work Seasonal pattern with 40% occurring in winter 7

8 Step : Questionnaire (Cont.) Programs: Wide range of practices Majority have training; much is informal Majority follow parts of AWWA Standard C65 or U.K. Technical Guidance Notes Issues: Pressure management Boil Water Advisories Featured Programs Fort Worth, TX Emergency response Leak detection procedures Excavation pit procedures Responses tied to type of break Flow chart for Boil Water Advisory (BWA) actions Los Angeles (LADWP), CA Pollution prevention Disinfection and dechlorination Training materials with quizzes Flushing protocols 8

9 Featured Programs (Cont.) New Jersey American Water Comprehensive Boil Water Advisory (BWA) guideline Boulder, CO Main break notification and communication protocols Charlotte-Mecklenburg, NC Training i materials and performance evaluations Denver, CO Flowchart for risk assessment Project Tasks Task : Define Terminology and Establish the Baseline of Practice Task 2: Conduct Laboratory, Pilot Studies and Risk Modeling. Microbial Risk Modeling 2. Flushing Effectiveness 3. Disinfectant Decay and Microbial Inactivation Task 3: Identify/Pilot Test Field and Monitoring Activities Task 4: Develop Tiered Risk Management Strategy Including Multiple Barriers Task 5: Prepare Work Products and Final Report 8 9

10 Microbial Risk Modeling (Concept). Pathogen levels in sewage (Meta-analysis of occurrence levels from literature) 2. Main breaks and depressurization (Sewage intrusion and dilution) 7. Risk management options a) Compare with an acceptable annual risk of 0-4 b) Flushing, disinfection, boil water advisory, etc. 3. Main break repairs and back to service: a) Flushing; b) Disinfection 6. Risk characterization (Monto-Carlo simulations in Mathematica 8.0) 5. Dose-response models (Collected from literature) 4. Individual water intake 9 Risk Model () Source of Contamination Overall 56% (8/32) of samples near water pipes were positive for viruses: enteroviruses, Norwalk, and Hepatitis A virus (Karim et al. 2003, JAWWA) Sewage Pathogen Levels Meta-analysis of occurrence levels in N=4 literature Pathogens/Indicator Geometric Mean Q0.025 Median Q Cryptosporidium E coli O57:H Norovirus Cryptosporidium

11 Invtrusion Vol (gal) Risk Model (2-4) Diameter (2) Intrusion Dilution 300 feet pipe pp depressurized Intrusion of gal of sewage Dilutions of 99 to 99.99% (3) Pathogen Levels after Main Break Repairs Removed by flushing Inactivated by disinfection Determined by lab studies shown in later slides (4) Individual Water Intake Unheated tap water intake from a population survey (Teunis et al. 997) Lognormal distribution with a median water consumption of 0.8 liter % 0.5% 5.% 5.06% % 0.23% 2.27% 22.69% 8 0.0% 0.3%.28% 2.76% 0 0.0% 0.08% 0.82% 8.7% 2 0.0% 0.06% 0.57% 5.67% % 0.03% 0.32% 3.9% % 0.0% 0.4%.42% % 0.0% 0.06% 0.63% % 0.00% 0.02% 0.6% Frequency 25% 20% 5% 0% 5% 0% Daily Water Consumption (L) 2 Risk Model (5) Dose Response Models Collected from literature Human feeding studies for various pathogens Determined the probability of infection ID 50 of8 viruses (dispersed) Percentage of Infected (%). 00% 80% 60% 40% 20% A single norovirus could cause infection in ~30% of population Best Fit Relation 95% Predictive Interval A single oocyst could cause infection in 2.8% of population 0%.0E-02.0E+00.0E+02.0E+04.0E+06.0E+08.0E+0 (a) Norwalk Virus Dose (# of viruses) 22

12 Risk Model (6-7) (6) Risk Characterization Monto-Carlo simulations (0,000 repetitions or more) During each repetition, random generated External pathogen levels Pathogen reduction by dilution, flushing, or disinfection Individual water intake Pathogen infectivity (7) Risk Management Options Baseline risk levels (dilution only) Risk levels after dilution + flushing Risk levels after dilution + flushing + disinfection 23 What are the baseline risk levels? Main break and depressurized Sewage intrusion % (i.e., 2-4 log of dilution) No flushing or disinfection Significant risks, especially from virus (Mean risk of 0.59).0E+00.0E+00.0E-0.0E-02.0E-0 Baseline - Dilution only Infec ctoin Risk--.0E-03.0E-04.0E-05 0E06.0E-06.0E-07 Infectoin Risk--.0E-02.0E-03.0E-04.0E-05 EPA Acceptable Annual Risk: /0,000.0E-08.0E-09.0E-0 EPA Acceptable Annual Risk: /0,000 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto).0E-06.0E-07 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto) Randomness of infection risks 24 2

13 How effective is flushing to reduce the risks? Pathogens attached to soil particles All suspended pathogens removed by flushing Assume flushed at a velocity above the threshold velocity and achieved 2-3 log removal Baseline - Dilution only.0e+00.0e+00.0e-0.0e-02.0e-0 Dilution + Flushing Infec ctoin Risk--.0E-03.0E-04.0E-05 0E06.0E-06.0E-07 Infectoin Risk--.0E-02.0E-03.0E-04.0E-05 EPA Acceptable Annual Risk: /0,000.0E-08.0E-09.0E-0 EPA Acceptable Annual Risk: /0,000 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto).0E-06.0E-07 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto) Infection risks reduced by 2-3 logs Flushing is effective, some risk may still remain high (e.g. mean risk of 0. for virus). 25 Flushing Results Sand Size Flushing kg of sand of difference sizes 2-4 mm; mm; and mm; Similar threshold velocities ( ft/sec) and removals ( log); 3.5 Flushing Sand Log Removal Log rem moval mm Sand mm Sand mm Sand Flushing Velocity (feet/sec) 26 3

14 How effective is disinfection to reduce the risks? What levels of disinfection will be needed for risk reduction? Disinfection had no reduction on the Crypto levels Need 4-5 logs of inactivation of virus and bacteria Baseline - Dilution only.0e+00.0e+00 Dilution + Flushing.0E-0.0E-02.0E-0 Dilution + Flushing + Disinfection Infec ctoin Risk--.0E-03.0E-04.0E-05 0E06.0E-06.0E-07 Infectoin Risk--.0E-02.0E-03.0E-04.0E-05 EPA Acceptable Annual Risk: /0,000.0E-08.0E-09.0E-0 EPA Acceptable Annual Risk: /0,000 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto).0E-06.0E-07 Virus (norovirus) Bacteria (E coli O57) Protozoa (Crypto) Virus and bacteria infection risks reduced by 4-5 logs, Crypto infection risk remained the same Mean risks of all three pathogens are below the /0,000 level. 27 Impact of Particle Shielding from Disinfection Suspended pathogens removed by flushing (no risk), soilattached pathogens control the risk Soil particles include Coarse-grained soils (e.g. sand, specific weight about 2.7) Fine-grained soils (e.g. silts and clays) Highly organic soils or peat (lightest of the three) Inactivation experiment of soil-attached pathogens Crypto resistant to free chlorine and chloramines Chloramine disinfection not effective for virus Experiments focused on chlorine disinfection of soil-attached virus and bacteria 28 4

15 Inactivation of Clay-Attached MS-2 and E Coli The effectiveness of chlorine disinfection slightly reduced 4-Log inactivation of clay-associated MS-2 and E coli need a higher CT of f74 and d92 mg/l /LCl* 2 *min Virus (MS-2) Clay provided slightly more protection from chlorine disinfection compared with sand. Bacteria (E Coli) tion Log inactiva Free chlorine inactivation of clay associated MS Observed Envelope CT (mg/l Cl2*minute) tion Log inactiva Free chlorine inactivation of clay associated E coli Observed Envelope CT (mg/l Cl2*minute) 29 Inactivation of Sand-Attached MS-2 and E Coli Log inactivation Virus (MS-2) Free chlorine inactivation of sand associated MS Observed Envelope CT (mg/l Cl2*minute) Log inactivation Bacteria (E Coli) Free chlorine inactivation of sand associated E coli Observed Envelope CT (mg/l Cl2*minute) Significant data variations, envelop used (conservative) The effectiveness of chlorine disinfection slightly reduced 4-Log inactivation of sand-associated MS-2 and E coli need a higher CT of 69 and 45 mg/l Cl 2 *min 30 5

16 Disinfectant Decay Frequency Histogram of Initial Chlorine Demand (n=59) More mg/l mg/l mg/l mg/l mg/l mg/l mg/l Initial Chlorine Demand (mg/l) Initial chlorine demands mostly 0-2 mg/l, up-to7mg/l Initial chloramine demands mostly less than mg/l N = 05 decay tests 25 Histogram of Initial Chloramine Demand (n=46) Ambient chlorine residual could be 5 overcome by water contamination 0 after main break depressurization, 5 while chloramine residual may still 0 remain. Frequency More mg/l mg/l mg/l mg/l mg/l mg/l mg/l Initial Chlorine Demand (mg/l) 3 Overall Main Break Risk Assessment (Conservative) Intrusion of raw sewage Leaking sewage nearby, worst scenario (compared with pit waters) Using sand as surrogate for flushing Sand is more difficult to flush, but provides minimal shielding from disinfection Lighter soil particles (e.g. peat) provide most protection, but easier to flush out. Flushing Using the CT of peat-attached virus for disinfection Sand or clay: 4-log inactivation CT values for free chlorine up to 92 mg/l Cl 2 *min Peat: 4-log inactivation CT values for chlorine up to,500 mg/l Cl 2 *min Risk Modeling Disinfection 32 6

17 Summary Site conditions and main break repair practices vary widely in the industry Age of infrastructure, rural versus inner city congestion, weather, soils, etc. There is a lack of a technical basis and risk management structure for assessing the effectiveness of mitigations such as flushing and disinfection Lab studies were conducted to evaluate pathogen removal efficacies by flushing and disinfection Background disinfectant residuals may either be overcome by water contaminations (free chlorine) or not provide adequate inactivation of pathogens (chloramines). A microbial risk model was developed to evaluate customer s infection risks after a main break and depressurization event Virus is the controlling risk (7-log reduction needed). Effective flushing would remove ~3-log particles and control the Crypto infection risk. Additional 4-log virus inactivation (disinfection) is needed to control the virus infection risk. Soil particles may protect virus from disinfection and 4-log inactivation CT values for free chlorine increase up to 00 mg/l Cl 2 *min. 33 Step 4: Risk Management Workshop April 8-9, 202 Mt. Laurel, NJ at American Water 30 participants from operating utilities, regulatory agencies, and the project team 3 7

18 Workshop Goals. Confirm the applicability of the risk model 2. Confirm the risk model input parameters (e.g., disinfectant concentration, flushing velocity) 3. Identify field activities for the next phase of the study 4. Discuss the applicability of this study as the technical basis for future revision of AWWA Standard C65 3 Key Results Developed four categories of main breaks Developed proposed response actions (procedures) for each type of break Identified field study objectives 3 8

19 Main Break Categories Type I Break Type II Break Type III Break Type IV Break Positive pressure Positive pressure Loss of pressure at Loss of pressure at maintained maintained during break during break break site/ depressurization elsewhere in system break site/ depressurization elsewhere in system Pressure maintained during repair Pressure maintained until break exposed Partially or uncontrolled shutdown Widespread depressurization No signs of contamination intrusion No signs of contamination intrusion Possible contamination intrusion Possible/ actual contamination intrusion 3 Type I Main Break Procedures Procedures Excavate to below break Maintain pit water level below break Repair under pressure Disinfect repair parts Check residual disinfectant level in distribution system No Boil Water Advisory (BWA) No bacteriological samples 3 9

20 Type II Main Break Procedures Procedures Excavate to below break Maintain pit water level below break Controlled shutdown Disinfect repair parts Conduct low velocity flush Check residual disinfectant level in distribution system No Boil Water Advisory (BWA) No bacteriological samples 3 Type III Main Break Procedures Procedures Uncontrolled shutdown Document possible contamination Disinfect repair parts Conduct scour flush (3 ft/sec min) Conduct slug chlorination (Ct of 00 e.g., 5mg/L for 20 min) Check residual disinfectant level in distribution system No Boil Water Advisory (BWA)* No bacteriological samples* *Based on risk model results, application of the proposed procedures, and acceptance by regulatory agencies 4 20

21 Type IV Main Break Procedures Procedures Catastrophic failure response Document possible contamination Shut-off customer services in affected area Disinfect repair parts Conduct scour flush (3 ft/sec min) Conduct slug chlorination (Ct of 00) Instruct customers to flush premise plumbing upon return to service Check residual disinfectant level in distribution system Issue BWA/ Boil Water Order Bacteriological sampling required 4 Main Break Triage 4 2

22 Next Steps Perform Field Testing Activities (202). Risk Flow Chart 2. Checklist / Field Form 3. Maintaining Pressure during Repair 4. Verification of Scour Velocity 5. Slug Disinfection vs Run-to-Ambient 6. Environmental Protection (Dechlorination) 7. Field Monitoring i (Chlorine) 8. Documentation Project Report (203) 4 Next Steps Perform Field Testing Activities (202). Risk Flow Chart 2. Checklist / Field Form 3. Maintaining Pressure during Repair 4. Verification of Scour Velocity 5. Slug Disinfection vs Run-to-Ambient 6. Environmental Protection (Dechlorination) 7. Field Monitoring i (Chlorine) 8. Documentation Project Report (203) Pocket Guide Update 4 22

23 Major Work Products Surveys & Case Studies Example SOP s of Best Practices Risk Based Management Strategy Final Report Technical Basis for New / Revised AWWA Standard 4 Questions Effective Microbial Control Strategies for Main Breaks and Depressurization Project 4307 Sponsored by Water Research Foundation and the U.K. Drinking Water Inspectorate May 24, 202 in association with 23