Chloramine Tips and Tricks for Operators

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Chloramine Tips and Tricks for Operators
City of Concord Matt Holmes WTP Operator
Marco Philippon WTP Superintendent

Concord’s Disinfection History
 1928 Disinfection with Free Chlorine starts.  1974 SDWA passes, the Concord WTP is constructed,
Disinfection still with Free Chlorine.  1995 With corrosion control, and disinfection degradation
in residuals at the ends of the system (nearly 150 miles of main at the time) Monochloramine added as a secondary disinfectant (1st in NH).

Intake Screens Bar rack

Penacook Lake

Disinfection optional


Primary Disinfection with Sodium Hypochlorite (Chlorine)
PH Adjustment & Fluoride

Raw Water Intake


Ammonium Sulfate




Clear Well

CO2 Addition

PH Adjustment

(Contact Chamber)


What Operators need to know and understand
 Why the ratio is important.  How to calculate the ratio.  How to calculate your chemical feed rate.  Adjust what needs to be adjusted.  What if’s?

Why is the ratio important?
 The creation of Chloramines happens when the weight ratio of Chlorine to Ammonia (Cl2 : NH3) is between 3:1 to 5:1. Anything over 5:1 will create dichloramine
 In excess of 5:1 can lead to water quality complaints.  The ideal ratio 1 molecule of Cl2, and 1 molecule of
NH3.  Chlorine weighs 5 times more than Nitrogen (70/14),
hence a perfect ratio is 5:1.

How to Calculate the ratio
 The standardized method for determining the chlorine to ammonia ration is:
 Chlorine Residual (Free) (mg/l as Cl2)
 Divided by…
 Ammonia Residual (mg/l as N)
Concord (typically)
 2.20 mg/l as Cl2 / 0.49 mg/l NH3-N = 4.5

How to calculate your chemical feed rate.
 Test Cl2 residual at point of injection (near).  Test for free Ammonia (target no more than .1 mg/l)  Perform a drawdown on Ammonia Pump. (Video)

Performing a chemical drawdown
 Equipment needed
 Calibrated Column  Proper valving to isolate tank from column.  Stop watch (something that will show seconds).
 Other pertinent data:
 Current flow rate in (MGD)  Chemical dosage equation


Matt’s Calculation check
 Known:  344ml in 1 minute (results of drawdown)  1440 Minutes in a day (60min. x 24hrs)  Approx. 3785 mls per gallon

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Chloramine Tips and Tricks for Operators