1. Directed Assistance Module (DAM) 8: Nitrification Action Plans (NAPs)
Developed by the TCEQ
Water Supply Division (WSD)
Texas Optimization Program (TOP)
Presented by the WSD
Financial, Managerial, and Technical (FMT) Capacity Development Contractor
v. 2

2. Outline of NAP DAM Presentation: Brief overview Six workshops
Sample Sites
Monitoring Frequency
Methods
Goals, baselines, and triggers
Actions
Communication strategies

3. Outline of Presentation
Chloramination
Nitrification

4. Chloramines

5. The chemicals of interestCl O - O H Cl
Chlorine
Regardless of gas or other source, in water it is hypochlorite ion and hypochlorous acid
Ammonia
“Free Available” ammonia
Inorganic (what is being dosed)
Organic (what is in some source water)
Chloramines: Mono-, Di-, Tri-
Monochloramine is what we want N H
Chloramine chemistry involves chlorine and ammonia, because those two chemicals react to form the chloramines.
Chlorine is well known to water system operators. Regardless of whether gaseous chlorine or aqueous hypochlorite solution is used, the chemicals present in water take the form of hypochlorite ion and hypochlorous acid.
Ammonia can be present in the desirable inorganic form, but organic ammonia is sometimes present in the source water.
Chlorine and ammonia react to form chloramines. The chloramine species that provides disinfection is monochloramine.
Decorative images: Sketches representing the molecules hypochlorite ion, hypochlorous acid, ammonium, ammonia, and monochloramine. H Cl N

6. Yuefeng Xie’s Bar Theory of chloraminationCl
This chlorine molecule walks into a bar…
At first, there are lots of free available ammonia molecules….
Later, a chlorine molecule walks into a bar…
And all the free available ammonia molecules were used up… N
Yuefeng Xie is a professor in Pennsylvania and also works providing assistance to small public water systems. He introduced the “Bar” theory of chloramination.
Image: Sketch of chlorine and ammonia atoms.

7. Chloramine chemistry HOCl + NH3  NH2Cl + H2O
NH2Cl + HOCl  NHCl2 + H2O
2 NH2Cl  NHCl2 + NH3
NHCl2 + HOCl  NCl3 + H2O
2 NH2Cl + HOCl  N2 + 3 Cl- + 3 H+ + H2O

8. Breakpoint curve Total Chlorine =
Total Chlorine Species
Cl2:N mass ratio 5: :1
Free Ammonia
Mono-chloramine
Dichloramine
Trichloramine
Free
Chlorine
Total Chlorine =
The sum of the active chlorine species
This graph is what we call the “breakpoint curve.” The vertical (Y) axis is the residual concentration for each chemical we are discussing. The horizontal (X) axis is the chlorine to ammonia-nitrogen mass ratio.
Image: Breakpoint curve graph

9. Breakpoint curve: Question
What CAN you measure?
Using normal equipment
Chlorine Residuals: Total and Species (mg/L)
Cl2:NH3-N (Chlorine to Ammonia-Nitrogen mass ratio)
Free
Ammonia
Mono-chloramine
Dichloramine
Trichloramine
Chlorine
Total
We have discussed the chemistry – now let’s consider the practical issue of what can and should be monitored for successful chloramination.
This graph is what we call the “breakpoint curve.” The vertical (Y) axis is the residual concentration for each chemical we are discussing. The horizontal (X) axis is the chlorine to ammonia-nitrogen mass ratio.
Image: Breakpoint curve graph

10. Nitrification

11. Nitrification
Nitrification happens when bacteria called nitrifiers ‘eat’ ammonia, then nitrite, to form nitrite, then nitrate.
Nitrification causes loss of residual chloramines.

12. The chemicals of interest
Normal chloramine reactions,
in the monochloramine zone:
HOCl + NH3  NH2Cl + H2O
2 NH2Cl  NHCl2 + NH3
Nitrification
NH3 + O2 AOB NO2-+ 3H+ + 2e-
NO2- + H2O NOB NO3- + 2H+ +2e-
The first two reactions are a subset of chemical equations for chloramines in drinking water.
The first reaction shows how combining chlorine (as hypochlorous acid) and ammonia reacts swiftly to form monochloramine and water. This is an equilibrium equation, so there is always a little ammonia and free chlorine present.
HOCl + NH3  NH2Cl + H2O
The second reaction shows that monochloramine can react with other monochloramine molecules to form dichloramine and ammonia. This reaction is called autodecomposition.
2 NH2Cl  NHCl2 + NH3
This shows that any time you have chloramination, you have some ammonia present from the equilibrium with monochloramine, and the autodecomposition of monochloramine.
If nitrifying bacteria are present, the next two reactions can occur. In the first, Ammonia Oxidizing Bacteria ‘eat’ ammonia to form nitrite. Then, Nitrite Oxidizing Bacteria ‘eat’ nitrite to form nitrate.

13. Nitrification in the environment
NITRITE (NO2-)
Nitrosomonas bacteria (AOB) uses up ammonia and makes NITRITE
PLANT FERTILIZER
AMMONIA
Wastewater effluent
Plant remnants
Fish excreta and urine
NITRATE
BUILD UP
Gases
ANAEROBIC BACTERIA
NITRATE (NO3-)
Nitrobacter bacteria (NOB) uses nitrite to make NITRATE
Run off
Plants and animals are part of the environmental nitrogen cycle
Ammonia enters the lake/river from waste: animal waste, discharged wastewater, plant remnants.
AOB change the ammonia to nitrite
NOB change the nitrite to nitrate
Some plants & benthic organisms, can change nitrate back to ammonia.
If the ecosystem is not balance, and unhealthy amount of nitrate can build up.
IMAGE: Animated image showing the nitrification cycle in the environment

14. Nitrification in a pipe
Nitrosomonas bacteria (AOB) uses AMMONIA to produce NITRITE
Nitrobacter bacteria (NOB) uses NITRITE to produce NITRATE
Reactions happen in biofilm
Naturally occurring
Decomposition of chloramines
AMMONIA
Added
NITRATE
BUILD UP
NITRATE (NO3-)
NITRITE (NO2-)
Things are a little different in a drinking water distribution system pipe.
First of all – there are no plants or animals.
But there will be some ammonia present if you are chloraminating.
You actually want to see a little ammonia so you know that you are in the monochloramine zone.
Also, there may be naturally occurring ammonia in your source water.
So the same set nitrification reactions can occur in the biofilm
Caused by the same organisms found in natural environments.
IMAGE: Animated image showing nitrification in a pipe.

15. Nitrification is an imbalance
There is a balance between how fast the chloramines can kill (“inactivate”) the bacteria and how fast the bacteria can regrow.
Nitrification is a problem when that balance shifts to where the bacteria are eating ammonia and growing too fast for the monochloramines to kill all of them.

16. Comparison of a Utility's operations during normal and nitrification events.
This example illustrates setting the triggers at Site #2 based on the data in the example we talked about earlier.
Clearly, at Site 2, a good residual goal is about 3 mg/L so we will set that as our goal.
And, we know that during nitrification, the level can drop to 1.0, so we will set the Red Flag goal with a bit of a safety factor at 1.5 mg/L.
Then – we can set a midpoint where we would be able to detect nitrification before it gets really bad.
If we had more data, we could do a better job of setting triggers.
Therefore, a PWS may modify the NAP as you get more data.
IMAGE: Graph of water quality parameters with and without nitrification.

17. NAP Workshops

18. A Nitrification Action Plan is like a Monitoring Plan
It includes
A sample site map,
Sample schedules,
Analytical methods,
Site-specific goals, baselines, and trigger levels,
Actions, and
Communication strategies.
A nitrification action plan will need to include:
A map showing sites—and their relation to storage, plants and so on,
Sample schedules,
Analytical methods,
The system’s site-specific trigger levels for the various sites, and
The actions that will be triggered.

19. DAM Workshops
This DAM includes a workshop for each element of the DAM.
As you go through each workshop, note follow-up actions that you will need to complete later.

20. Workshop 1. NAP sites NAP sample sites:
Represent sources, entry points, average and high water age in all pressure planes.
Can be the same as coliform sites
But they don’t have to be.
Critical control points
“A point where control can be applied and is essential to prevent or eliminate nitrification”
EG: Before booster chloramination

21. Workshop 2. Monitoring frequency
NAP monitoring must be done weekly,
May be done more frequently.
Small systems, <750 people or 250 cnx.
Monitor monochloramine and ammonia with every weekly total chlorine sample.
Large systems, select sites at low, average and high water age for weekly sampling.

22. 3a. Sample collection method
Water representing the main
Not stagnant water in the sample line
Use the calculated flush time (CFT)
Based on volume and flow
Flush just two (2) pipe-volumes
Don’t overflush
Consider building a hydrant and tap sampler

23. 3b. Analytical methods Total chlorine:
Use EPA approved method
Monochloramine, ammonia, nitrite, nitrate
EPA does not have approved methods.
Achieve the required accuracy
Document on the List of Analytical Methods (LAM)
Attach to Monitoring Plan

24. 4. Goals/baselines and trigger levels
Nitrification is controlled by defining what “normal” is and looking for trends that are “abnormal.”
Therefore, initial data must be analyzed to define normal levels,
And additional data must be analyzed or hypothetical levels must be projected for levels that are a concern: trigger levels.

25. Comparison of a Utility's operations during normal and nitrification events.

26. Workshop 5. Actions! Preventive action: Corrective: Trigger 1
Routine operating conditions
Do this even when your levels are ok
Corrective: Trigger 1
Intermediate--Do this when levels are not quite ok
Corrective: Trigger 2
Do this when nitrification is bad
Preventive actions are the things you normally do, even when your levels are ok.
For example, you change your oil even if the car is not running poorly.
You will take minor corrective actions when a minor –Yellow- trigger level is detected.
For example, if normal flushing does not bring residuals up enough, you will flush longer.
Major corrective action may be needed when a major – Red – trigger level is detected.
For example, when you have bad nitrification, you may consider a free chlorine burn.

27. Most preventive and corrective actions overlap
Verify results.
Flush.
Dose chlorine and ammonia correctly.
Minimize water age.
Operational corrective action:
Temporary conversion to free chlorine.
As a brief overview, preventive and corrective actions, include:
For systems who dose chloramines, controlling the chlorine to ammonia ratio is the first step. Additionally, adequate mixing is important.
Second, closely tracking the chloramine effectiveness parameters in distribution will give you the information to take action to avoid nitrification.
Anything you do to control water age will also be helpful.
Likewise, all of your efforts to keep distribution pipes clean will help.
When an event is occurring, there are fewer options.
The first thing folks do is flush, to try and bring fresh water with a good chloramine residual into the affected area. For a minor event, this can work.
For more extensive events, the corrective action is to refresh the distribution by converting to free chlorine. This is the most effective reaction for an event, but it can also be used as a preventive strategy. Free chlorine starves the nitrifiers of ammonia.

28. Workshop 6. Communication strategies
Make sure that all communication pathways are robust:
Standard operating procedures
Chain of command for action approval
Notification of other PWSs, customers, TCEQ as needed.

29. Example: Nitrification Action Plan
Nitrification Action Plan Example
Chloramine-Effectiveness Sample Suite
Site
Chemical
Goal
Yellow Flag
Red Flag
Trigger
Actions
Entry Point
Total / Mono
4.2
3.5
1) Verify results 2) Check and adjust dose ®Till levels return to normal
3.0
1) Verify results 2) Adjust dose ®Till levels return to normal
Free ammonia
0.01
0.2
0.3
Average Water Age
2.0
1.5
1) Verify results 2) Measure nitrite and nitrate 3) Adjust dose 4) Identify affected area (check upstream and downstream) 5) Flush area 6) Flush dead ends ®Till levels return to normal
1.0
1) Verify results 2) Measure nitrite and nitrate 3) Adjust dose 4) Identify affected area (check upstream and downstream) 5) Flush area 6) Flush dead ends 7) Convert to Free Chlorine ®Till levels return to normal
+/- 20%
+/- 50%
High Water Age
0.7
0.5
Nitrite/Nitrate
Baseline
Nitrite
0.025
+/- 20% (<0.02 or >0.03)
1) Verify results 2) Identify source changes IF confirmed-modify BL 3) Identify area, 4) Flush area ®Till levels return to normal
+/- 50% (<0.013 or >0.05)
1) Verify results 2) Identify affected area 3) Flush 4) Perform free chlorine burn ®Till levels return to normal
Nitrate
>1.7
>2.0
Source water(s)
Blended water
Example: Nitrification Action Plan
This is an example of a Nitrification Action Plan in the form of a table.
It captures the goals for total, mono, and ammonia at low, medium, and high water age.
It also recognizes the baseline levels for nitrite and nitrate
It sets trigger levels for moderately off-spec water and extremely off-spec water.
And finally, it lists actions to take under those conditions.
In addition, a NAP may include triggers for pH or other parameters.

30. Take-home Message
Finally, our conclusions.

31. Take-home Message Chloramines are an important tool.
They can help maintain residuals, and
Avoid unwanted disinfection byproducts.
Nitrification is a potential risk of chloramination.
Nitrification can be detected and controlled using a Nitrification Action Plan
For Texas water systems, chloramines can really help to control disinfection byproducts and maintain a long-lasting residual.
It is true that nitrification is a potential concern.
But if a system plans for that concern, the negative consequences of nitrification can be avoided.