Nitrification TCEQ. Public Drinking Water Conference Austin, Texas August 16, A System s Perspective after 20 years of Chloramination

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Hector Lawson
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1 Nitrification A System s Perspective after 20 years of Chloramination Presented by: Daniel K. Nix Water Source/Purification Superintendent City of Wichita Falls Public Drinking Water Conference Austin, Texas August 16, 2006 TCEQ

Nix Water Source/Purification Superintendent City of

2 Wichita Falls Overview Population 106, Total Trihalomethane Rule THMFP = < 15 min 1979 TTHM Violation (>200 ppm TTHM)

3 Chloramines The Switch Switched to Chloramines in Used Anhydrous Ammonia Initially fed NH 3 upstream of 4:1 ratio TTHM s dropped to below 10ppm. Life was Good. Monochloramine NH 2 CL

upstream of Chlorine @ 4:1 ratio TTHM s dropped

4 The First 10 Years Don t Look for IT and we won t have to Deal With It.

5 After the First 10 Years August Elevated Storage Tank 0.0 Total Chlorine Residual Investigation Found: 3.5 ppm TC into EST 0.0 ppm TC out of EST EST not being drawn-down. Recommendations: Add HTH to tank. Cycle water in EST to half full before re-filling.

5 ppm TC into EST 0.0 ppm TC out of EST EST not being drawn-down.

6 The Second 10 Years Began educating ourselves about Nitrification. Implemented a program of all Elevated Storage Towers being drawn down to half-full before they were actively filled back up. Monitored the EST s in far reaches during the summer months and flushed when necessary. Life was Good, Again.

half-full before they were actively filled back up.

7 The Second 10 Years However, problems still occurred from time to time. Wholesale customers calling about low/non-existent Total Chlorine residuals. Sporadic Total Chlorine residuals within the far reaches of the Distribution System. And Then Came,.

8 Pink Chicken One fried chicken store having recurring problems. Found to be on a dead-end line. Implemented Flushing program for the dead-end. Nitrate/Nitrite formation from Nitrification reacted with the chicken (myoglobin) to produce a pink color upon cooking. Pinking

9 The Second 10 Years Same problems throughout the 90 s, same solutions. Flush Area in Distribution System Cycle Towers Late 90 s saw Drought conditions. Increased Water Temperature Water Conservation Efforts Spawned Increased Detention Times within Distribution System Increasing Problems, but still Manageable.

10 Drought Persisted The Third 10 Years Conservation Efforts very Successful Unfortunately, in 2002, the Nitrifying Bacteria were in Nitrifying Heaven Losing Disinfectant Residual all over the City. Nitrate & Nitrite Concentrations Increasing. ph Decreasing with Low Alkalinities.

Nitrifying Heaven Losing Disinfectant Residual all over the City.

11 Conventional Warfare Evaluated the options that were available and decided to a multifaceted approach; Checked Chlorine to Ammonia ratios. Adjusted ph to 9.0 at Plant Discharge. Flushed the worst areas affected. Took all of the EST s to zero level and re-filled.

Ammonia ratios. Adjusted ph to 9.0 at Plant Discharge.

12 Results After 7 days, the initial results were positive. Chloramine Residuals were up from <1.0 ppm to >1.5 ppm. Nitrate/Nitrite Concentrations were cut in half, but were remaining high and persistent. Had gone as far as we could with this approach.

Nitrate/Nitrite Concentrations were cut in half, but were

13 The Nuclear Option The decision was made to convert to Free Chlorine. Pros; Works amazingly well, by removing the food source Works amazingly quick. Within 24 hours, no Nitrifying affects seen in the Distribution System.

14 The Nuclear Option However, it does come with some down sides. Cons; Notify, Notify, Notify. Change CT calculations and train staff. Increased Trihalomethanes Staff had forgotten the finer points of practicing Breakpoint Chlorination.

15 End of the Episode After running Free Chlorine for 4 days, the system was switched back to Chloramines. Significant changes were implemented to the way the Purification staff operated and the way the Distribution System was monitored. Life was Good, Again.

Significant changes were implemented to the way the

16 Food Source Current Plant Practices Plant now takes into account the optimum growth characteristics for Nitrifying Bacteria. Staff uses Temperature as the Trigger for Nitrifying Treatment Procedures. Optimize the Chlorine / Ammonia Ratio Ammonia Concentration in Raw Water Environment Adjust ph in Discharge to 9.0

Staff uses Temperature as the Trigger for Nitrifying Treatment Procedures.

17 Current Distribution System Practices Within the Distribution System; Elevated Storage Towers are cycled to lower levels, more frequently and not filled as full. Dead-Ends are routinely looped or flushed. Monitoring Temperature ph / Alkalinity Nitrate / Nitrite Chloramine Decay Bacteriological Analysis

filled as full. Dead-Ends are routinely looped or flushed.

18 Today Since 2002, the City of Wichita Falls has not experienced any significant problems with Nitrification within the Distribution System. The Nitrification protocols continue to be evaluated on an annual basis and changes made accordingly.

19 Message for System Switching to Chloramines Your system WILL experience Nitrification. Develop the necessary tools NOW to help minimize and/or prevent its occurrence. Don t Ignore the Problem, when it occurs.

20 Thank You Questions / Answers

EPB 311- Strategies for Dealing with Groundwater Treatment Systems Having High Natural Ammonia

EPB 311- Strategies for Dealing with Groundwater Treatment Systems Having High Natural Ammonia Background The occurrence of ammonia (NH 3 ) in the water source is often associated with pollution due to