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

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

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

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

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

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

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

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

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

Literature Review Newest CDC Surveillance For Waterborne Disease Outbreaks 2009-2010 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

Literature Review Newest CDC Surveillance For Waterborne Disease Outbreaks 2009-2010 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

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

-------------------------------------------------------- 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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