1. Optimizing Chlorine Flush
Ali Bayat, P.E.
Palm Beach County Water Utilities

2. Outline Objective Why Chlorine Flush System Description
Literature Review
Data Review
2013 Flush
Observations
Conclusions and Recommendations
Optimizing Chlorine Flush
4/8/2019

3. Objective
To evaluate the effectiveness of annual chlorine flush program and provide recommendations for improvements
Specific goals;
Evaluation of the effect of chlorine flush on water quality,
Review of reduction in flushing activities, and
Evaluation of annual chlorine flush duration
Optimizing Chlorine Flush
4/8/2019

4. Why Chlorine Flush
To maintain water quality by minimizing the bacterial/chemical activities such as nitrification in distribution system
Also to remove sediments and biofilms from the pipes (if water moves with a minimum velocity of 3 ft/s)
Optimizing Chlorine Flush
4/8/2019

5. Why Chlorine Flush
What advances the growth/re-growth of bacteria and microbes?
Contamination
Insufficient disinfectant residual level
High presence of organic material
Biofilm
Factors Effecting Biofilm Accumulation
(Ollos et al, 2003)
Residual
Organic matter
Flow velocity
Pipe material
Temperature
Factors Effecting Biofilm Accumulation
(Ollos et al, 2003)
Residual
Organic matter
Flow velocity
Pipe material
Temperature
Optimizing Chlorine Flush
4/8/2019

6. System Description Over 500,000 customers
Annual average daily flow of 60 MGD
Five water treatment plants
Three membrane plants
Two lime softening/ion exchange process
Over 2,300 miles of water mains
Optimizing Chlorine Flush
4/8/2019

7. System Description Lime Softening /Ion Exchange Membrane Systems
Optimizing Chlorine Flush
4/8/2019

8. Literature Review Chlorine vs. Chloramines
Monochloramine
Raw Water
(wells)
Chloramines
Free Chlorine
Hypochlorite Ion
Treatment
Process
Dichloramine
Hypochlorous Acid
Ammonia
Chlorine
Trichloramine
Both generate halogenated DBPs
Nitrogenous DBPs may be an issues with Chloramines
Free Chlorine is a stronger oxidizer and more effective
on AOBs and HPCs bacteria
Chloramines last longer and more effective on some
opportunistic microorganism like Legionella
Optimizing Chlorine Flush
4/8/2019

9. Dominant form: Dihaloacetic acids Dominant form: Chloroform
Literature Review
Halogenated Organic Byproducts
Chloramination
Less TOX, THMs and HAAs
Known DBPs 20% of TOX
Dominant form: Dihaloacetic acids
Chlorination
More TOX, THMs and HAAs
Known DBPs 50% of TOX
Dominant form: Chloroform
Optimizing Chlorine Flush
4/8/2019

10. Literature Review Newest CDC Surveillance For Waterborne
Disease Outbreaks
Legionella accounted for 58%
of outbreaks
Legionella pneumophila (currently in CCL3);
found in the environment
including hot water systems
causing lung diseases when
inhaled
Optimizing Chlorine Flush
4/8/2019

11. Literature Review Newest CDC Surveillance For Waterborne
Disease Outbreaks
Most commonly outbreak deficiencies were Legionella in;
plumbing systems (58%),
untreated ground water (24%), and
distribution systems (12%).
Studies have shown that Chloramines are very effective on Legionella
Weintraub et al, 2008
Pryoer et al, 2004
Heffelfinger et al, 2003
Kool et al, 1999b
Optimizing Chlorine Flush
4/8/2019

12. Literature Review Faster reaction Nitrification Ammonia AOB Bacteria
(Dominant form: Nitrosomonas)
Nitrites
NOB Bacteria
(Dominant forms: Nitrospira, or Nitrobacter )
Nitrates
Optimizing Chlorine Flush
4/8/2019

13. --------------------------------------------------------
Literature Review
Growth of Nitrifiers
Chlorine + Ammonia Chloramines
Ammonia Chloramines
Others + Ammonia Chloramines
NH3 + O2 + HCO3- + P +Trace Nutrient
NO2-+ NO32- + Organic C + …
Optimizing Chlorine Flush
4/8/2019

14. Alkalinity and pH Decrease Nitrite & Nitrate Production
Literature Review
Nitrification Effects Summary
Nitrification
Alkalinity and pH Decrease
Nitrite & Nitrate Production
Organic C Production
Corrosion
Imposed Disinfectant Demand
Support Bacterial Growth
Optimizing Chlorine Flush
4/8/2019

15. Literature Review Signs of Nitrification To Avoid Nitrification
Disinfectant Residuals
Free Ammonia
Nitrite/Nitrate
HPCs
Alkalinity/pH
Temp
To Avoid Nitrification
Parameters
Limits (mg/L)
TCR
>1.5
Free Ammonia
<0.1
Nitrite
<0.05
HPCs
<500 pH
8.2-9
Optimizing Chlorine Flush
4/8/2019

16. Literature Review
Dr. Marc Edward, Water Research Foundation Project#4015
Optimizing Chlorine Flush
4/8/2019

17. Literature Review Prediction of Nitrification
Nitrification Potential Curve (NPC; Fleming et al, 2005, 2008)
Nitrification Index (NI; Speitel et al, 2011)
The NI is a ratio of AOB growth and inactivation rates which the inactivation rate is the sum of;
Endogenous decay,
Chloramines inactivation, and
THM cometabolism product toxicity (Karen et al, 2013)
-Chloroform, Bromoform, Bromodichloromethane, and Dibromochloromethane
Optimizing Chlorine Flush
4/8/2019

18. Data Review Statistical Review Hot Spots Regression Analysis
Geostatistical Analysis
Optimizing Chlorine Flush
4/8/2019

19. Data Review
Statistical Review
Optimizing Chlorine Flush
4/8/2019

20. Data Review Demands Water Age Residuals Nitrite + Nitrate HPCs
Free Ammonia pH
Temp
Optimizing Chlorine Flush
4/8/2019

21. Complaints Hot Spots Analysis
Data Review
Customers Feedback
Color
Taste
Odor
Complaints Hot Spots Analysis
Optimizing Chlorine Flush
4/8/2019

22. Data Review Chlorine Flush Effectiveness Optimizing Chlorine Flush
4/8/2019

23. Data Review Chlorine Flush Effectiveness Optimizing Chlorine Flush
4/8/2019

24. Data Review Flushing Activities Reductions
Also other factors were involved such as improvements in TOC removal at the plants
Optimizing Chlorine Flush
4/8/2019

25. 2013 Annual Flush
Staff meetings and conducted to identify problematic areas and exploring new effective ideas
Water quality data analysis including Chlorine residual, HPCs, Free Ammonia and Nitrite + Nitrates performed
Hydraulic modeling performed to identify areas with high water age and dead ends
A new specific plan for attacking the target areas developed
Optimizing Chlorine Flush
4/8/2019

26. 2013 Annual Flush
Daily monitoring of the Free Chlorine levels leaving the plants and re-chlorination facilities (Mecca and P&W)
Daily review of flushing activities and Free Chlorine levels in distribution including line and valve crew as well as lab results
Monitoring customer feedbacks
Optimizing Chlorine Flush
4/8/2019

27. 2013 Annual Flush Day 1 Day 2 Day 3 Day 4 Day 7 Day 9
Optimizing Chlorine Flush
4/8/2019

28. Observations It took about a week to finish all six groups
Depend on the location, a good free residual, above 1.0 mg/L, was observed between 1 to 7 days after flush started
Few locations showed fluctuations in the results. It is concluded that this is mostly due to the problems in distribution system such as closed valves or high water ages
Optimizing Chlorine Flush
4/8/2019

29. Conclusions & Recommendations
Staff training is a key element to the program success. They need to fully understand;
Why
How
Program results and success
While performing a systemwide flush, the focus should be on the problematic areas which needed to be identified prior and effectively addressed during the flush
Optimizing Chlorine Flush
4/8/2019

30. Conclusions & Recommendations
To minimize complaints the residual concentration leaving the plants should be monitored closely and adjusted accordingly
Performing uni-directional flushing or pigging in areas suspected for established bio-films or sediments may be needed
The optimization of Chlorine Flush duration and frequency is case specific and should be evaluated based on several factors such as water quality, feasibility and customer acceptance
Optimizing Chlorine Flush
4/8/2019

31. 2013 Flush-Conclusion
Thank you Q?
Optimizing Chlorine Flush
4/8/2019