1. Chloramination 101
Scott Kahle
ASA Analytics

2. Optimizing Chloramine Treatment AWWA Research Foundation
Technical Sources
Optimizing Chloramine Treatment
AWWA Research Foundation
1993 and 2004
AWWA and EPA Web sites
Laboratory Experiments and Experiences at Hundreds Chloramination Facilities

3. Chlorination + + Chlorine
Pathogens
Safe Water
Chlorine
Hypochlorous Acid + +
Hypochlorite
Chlorine has prevent the spread of waterborne diseases such as cholera, dysentery, typhoid etc ….

4. Chlorination First use for Water Disinfection in late 1800’s Benefits:
Strong oxidizer for disinfection
Persistent residual to the tap
Disadvantages:
Strong oxidizer that reacts with many inorganics and organics
Under some conditions, decays rapidly

5. Disinfection Byproducts - DPBs
Hypochlorous Acid (HOCl)
Natural Organic Matter (NOM)
THM and HAA
(Carcinogens) + +
Strong Oxidizer

6. DBP Reduction
Remove Organic Precursors that are reactive with chlorine (filters, membranes, ion exchange, etc… remove TOC )
Decrease the amount of hypochlorous acid available in the reaction (this can be accomplished via chloramination)
Decrease the time of contact between the organic material and hypochlorous acid (also accomplished via chloramination)

7. Chloramine Formation NH3 + HOCl NH2Cl + H20 Monochloramine
Monochloramine + HOCl NH2Cl + H20
Dichloramine
(Strong Order
Weak Disinfectant)
Dichloramine HOCl NCl3 + H20
Trichloramine
(Strong Order and Taste
Weak Disinfectant)
Organo-chloramines are can also be formed in the presences of organics

8. Chloramines vs Chlorine
More Stable - Longer Lived Residuals
Less Reactive (reduced DBP formation)
Minimizes Objective Taste and Odor (As long as Dichloramine and Trichloramine are not produced)

9. Disinfection Byproducts
Natural Organic Matter (NOM)
Minimal DBPs
Monochloramine + +
Weaker Oxidizer

10. History of Chloramines
Initially used in the early 1900s when it was found that chlorine-ammonia addition could save cost by reducing chlorine used.
First recognized Chloramination WTP in North America – Ottawa, Ont. In 1916.
First US Chloramination WTP – Denver, Colorado in 1917 to improve taste.

11. History of Chloramines (Cont.)
By 1938 – more than 400 utilities chloraminating.
Practice reduced during WWII due to shortage of ammonia.
1970s – THMs were discovered to be a health threat. Chloramines used to reduce THM formation.
Regulations balancing risk from microbial contamination and risks of disease from DPBs.
1998 Stage 1 Disinfectant/DBP Rule
2006 Stage 2 Disinfectant/DBP Rule

12. Conversion to Chloramination at Some Cities (approx)
Denver, CO
Portland, OR
Massachusetts Water Resources Authority
St. Louis, MO
Portland, ME
Boston, MA
Minneapolis, MN
Dallas, TX
Kansas City, MO
Miami, FL
San Diego, CA
Currently more than 1500 Utilities use chloramination in the U.S.

13. Chloramination Basics
Applied Chlorine Dosage (mg/L)
Zone 1
Zone 2
Zone 3
Zone 4
1.0 mg/L NH3-N, pH 7, temperature 25 C, contact 2 hours
Available Residual Chlorine (mg/L)
The Dreaded “Breakpoint Curve”

14. Relative Chlorine Demand of Some Compounds:
Zone 1
Zone 2
Zone 3
Zone 4
Zone 1: Initial chlorine demand is met: Chlorine is oxidizing reactive chemical constituents.
Relative Chlorine Demand of Some Compounds:
Fe = 0.64 mg/l NH3 = mg/l
Mn = 1.30 mg/l Org-N = 1.00 mg/l
NO2 = 5.00 mg/l TOC = 0.10 mg/l

15. Zone 1
Zone 2
Zone 3
Zone 4
Zone 2: Chloramines are forming up to an approximate ratio of 5:1 (Five Parts Chlorine to One Part Ammonia by weight).
NH HOCl NH2Cl + H20
Monochloramine
Weight:

16. Zone 1
Zone 2
Zone 3
Zone 4
Zone 3: No free ammonia available - Dichloramines and Trichloramines are formed as the ratio exceeds 5:1
NH2Cl + HOCl NHCl2 + H2O
Dichloramine
NHCl2 + HOCl NCl3 + H2O
Trichloramine

17. Zone 1
Zone 2
Zone 3
Zone 4
Zone 4: Breakpoint - Free chlorine residual is now being created. For every 1.0 mg/l of chlorine added, the residual will increase 1.0 mg/l. Some Organo-chloramines and Trichloramine still exist.

18. How Fast Are Chloramines Made?pH
Time (Seconds) 4
147 7
0.2
8.3
0.069 12
33.2

19. Chloramine Species with pH

20. Cl2:N Ratio Effects on THM and Flavor

21. Optimal Chloramination Control Range
This graph represents the optimal control range of monochloramine when comparing it to the formation of flavor and total trihalomethanes.
The upper graph is the breakpoint curve. As we get to the peak of that curve it is at a point where we have very little free ammonia and also our flavor and trihalomethanes formation is at a minimum.

22. Nitrification + + Ammonia Oxidizing Bacteria (AOB) Nitrosomonas
Nitrite Oxidizing Bacteria
Nitrobacter
Ammonia
NH3
Nitrite
NO2
Nitrate
NO3 +
Dissolved
Oxygen O2
Dissolved
Oxygen O2 +

23. Nitrification Impact
Nitrification occurs when disinfection concentration is low.
It can result in a lowering of pH, increased corrosion and/or depletion of Dissolved Oxygen.
For every 1.0 mg/l of NO2 (Nitrite) formed, 5.0 mg/l of chlorine are needed to oxidize.
Nitrification typically results in the further reduction disinfection residual causing a downward spiral.

24. Nitrification Control
Maintain Higher Chloramine Residual
Higher Cl2 : NH3-N Ratio (less Free NH3)
Maintain Higher pH
Periodic Chlorine Shocks
Higher Turnover and/or Mixing in Reservoirs
System Flushing
Monitoring at Strategic Locations and Boost Chlorine

25. Chloramination Control Challenges
Maintain Adequate Disinfectant Concentration to Ensure Safe Water
Feed Enough Ammonia to Prevent Di and Trichloramine Formation and Prevent Drop in Chlorine Residual
Prevent Over Feed of Ammonia to Minimize the Potential of Nitrification in the Reservoirs and Distribution System
On-Line Analysis Provides the Information Required to Control the Chloramination Process

26. Breakpoint as Measured by Free and Total Chlorine Analyzers
A Total Chlorine result has 3 possible locations on the breakpoint curve
Free Chlorine test reacts with Monochloramine giving a false reading until beyond the Breakpoint
First Indication of Free Chlorine is AFTER Dichloramine Formation
Some municipalities attempt to use free and total chorine analyzers to control their chloramination process – with limited success.
A total chlorine analyzer results in three possible locations on the breakpoint with no indication of which you are at.
Free chlorine reacts with monochloramine giving false reading until beyond the breakpoint. First indication of free chlorine is after dichloramine formation.

27. Break-point Curve as Read on On-Line Analyzer
At ratios below 5:1, Total Chlorine and Monochloramine values are equivalent
Between the ratios of 5:1 and 8:1, Total Chlorine is greater than Monochloramine as Dichloramine is formed
At ratio greater than 8:1, Free Chlorine is present
At ratios below 5:1, Total Ammonia remains constant as Free Ammonia decreases until reaching 5:1
At ratios greater than 5:1, Total Ammonia decreases and free ammonia is near zero
Here is the breakpoint curve as read on the ChemScan Analyzer
In this case a .6 mg per leader ammonia sample was dosed with increasing levels of chlorine.
At ratios below 5:1, Total Chlorine and Monochloramine values are equivalent
Between the ratios of 5:1 and 8:1, Total Chlorine is greater than Monochloramine as Dichloramine is formed
At ratio greater than 8:1, Free Chlorine is present
At ratios below 5:1, Total Ammonia remains constant as Free Ammonia decreases until reaching 5:1 ratio
At ratios greater than 5:1, Total Ammonia decreases and free ammonia remains near zero

28. Why is Chloramination so Difficult?
Applied Chlorine Dosage (mg/L)
Varying NH3-N, pH 7, temperature 25 C, contact 2 hours
Available Residual Chlorine (mg/L)

29. Simplified Drinking Water Process
Post Chlorination Ammonia Feed
Cl2
Analyzer
Cl2
Analyzer
FNH3, TNH3, Mono
and TCl2 Analyzer
Total Cl2
Goal
3.0 mg/L
Wet Well
Mixer
Free NH3-N
Cl2
Feed
0.05 mg/L
0.14 mg/L
0.22 mg/L
Cl2
Trim
NH3
Feed
Weight Ratio Cl2 : NH3-N
Free Cl2
3.0 mg/L
4.8:1
3.4 : 1
3.7:1
4.2:1

30. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.0 :1
FNH3
0.22 mg/L
TNH3
0.99 mg/L
Mono
2.90 mg/L
TCl2
2.94 mg/L
DIChor
0.04 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

31. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
3.7 :1
FNH3
0.11 mg/L
TNH3
0.77 mg/L
Mono
2.89 mg/L
TCl2
2.93 mg/L
DIChor
0.04 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

32. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
4.6:1
FNH3
0.04 mg/L
TNH3
0.64 mg/L
Mono
2.93 mg/L
TCl2
2.97 mg/L
DIChor
0.04 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

33. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
5.0:1
FNH3
0.02 mg/L
TNH3
0.59 mg/L
Mono
2.9 mg/L
TCl2
2.97 mg/L
DIChor
0.07 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

34. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
6.3:1
FNH3
0.02 mg/L
TNH3
0.44 mg/L
Mono
2.38 mg/L
TCl2
2.79 mg/L
DIChor
0.41 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

35. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
6.5:1
FNH3
0.02 mg/L
TNH3
0.27 mg/L
Mono
1.33 mg/L
TCl2
1.74 mg/L
DIChor
0.27 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

36. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
7.7 :1
FNH3
0.02 mg/L
TNH3
0.02 mg/L
Mono
0.13 mg/L
TCl2
0.16 mg/L
DIChor
0.03 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

37. Breakpoint with Fixed Cl2
Free Cl2
3.0 mg/L
Ratio
3.4:1
8.8 :1
FNH3
0.02 mg/L
TNH3
0.02 mg/L
Mono
0.14 mg/L
TCl2
0.74 mg/L
DIChor
0.03 mg/L
Here is a breakpoint curve where the chlorine is fixed and the ammonia is varied.
In this case we’ve chosen a 3mg per liter chlorine dosage and the ammonia is decreased in prepared samples. While the ratio is less than 5:1 the total chlorine and monochloramine are equivalent until while we reach the 5:1 ratio where they begin to separate as dichloramine is forming. The total ammonia decreases as the graph goes from left to right indicating the dosage of the total ammonia. The free ammonia begins at an elevated level and decreases to near zero at the 5:1 ratio.

38. Optimal Control

39. Chloramination Control Strategies
Ratiometric control
Cl2 : NH3-N ratio between 3:1 and 5:1
Measures total chlorine from all forms and total ammonia from all forms (free and combined)
Residual control
Maintain target monochloramine or total chlorine
Maintain small free ammonia residual

40. Chloramination Feed Options
Post Chlorination Ammonia Feed
Cl2
Analyzer
Cl2
Analyzer
FNH3, TNH3, Mono
and TCl2 Analyzer
Wet Well
Mixer
Cl2
Feed
Cl2
Trim
NH3
Feed

41. Chloramination Feed Options
Simultaneous Chlorine Ammonia Feed
NH3
Feed
FNH3, TNH3, Mono
and TCl2 Analyzer
FNH3, TNH3, Mono
and TCl2 Analyzer
Wet Well
Mixer
Mixer
Cl2
Boost
(Optional)
Cl2
Feed

42. On-Line Chloramination Analyzers
ChemScan UV-Series –
FNH3, TNH3, Mono, TCL2 and UV254
Multiple Sample Lines
ChemScan Multi-mini -
FNH3, TNH3, Mono and Ratio
ChemScan Single Parameter -
mini-FNH3, mini-TNH3, mini-Mono and mini-Chlor

43. Case Study I Full Scale Pilot Study
Reservoir converted from Free Chlorine to Chloramines

44. Chloramination Process Out of Control
Free ammonia either too high or too low
Chlorine Levels unstable

45. Chloramination Process Out of Control
When free ammonia is greater than zero, total chlorine tracks with monochloramine
When free ammonia is zero, total chlorine is greater than monochloramine indicating formation of dichloramine

46. Chloramination Process - In Control
- Free Ammonia level constantly above detection limit but low enough to reduce nitrification potential (ave 0.05 mg/L)
Total Chlorine and Monochloramine are very close in value and stable

47. Summary Chloramines are Effective Disinfectants
Chloramination can be Difficult to Control
Too little ammonia cause di and trichloramine formation and loss of chlorine residual
Too much ammonia can cause nitrification in reservoirs and distribution system
Proper Distribution System Management starts with minimizing free ammonia at the plant
Distribution System Boosting of Chlorine (and ammonia) is key to keep disinfectant concentration optimized
Effective On-Line Analysis Equipment will Aid in the Control of the Chloramination Process

48. Questions