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CHLORINATIONCHLORINATION
Chlorination Curve
• What happens when chlorine is added to water?– A chlorination curve will help describe what
happens during this process
Chlorination Curve
• What is a chlorination curve?– A graph of the amount of chlorine measured
in a solution versus the amount of chlorine added
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
Chlorination Curve
• Begin adding chlorine to water– Chlorine will first react to exhaust chlorine
demand in the system– Chlorine added will not be recovered in a
chlorine test
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
Chlorination Curve
• Continue adding chlorine to the system– Once chlorine demand is exhausted,
additional chlorine added will be recovered in a chlorine test
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
Chlorine Testing
• Chlorine - Free & Total– DPD chlorine reagent powder pillows or
AccuVacs (EPA approved)• Pocket Colorimeter II• DR/800• DR/2800• DR/5000
CHLORAMINATIONCHLORAMINATION
Chloramines
• Chloramines are formed when free chlorine reacts with free ammonia present in the water – Monochloramine (NH2Cl)– Dichloramine (NHCl2)– Trichloramine (NCl3)
Chloramination Curve
Chlorine Added
Chl
orin
e M
easu
red
Chloramination Curve
• Begin adding chlorine to a water containing ammonia– Initial addition of chlorine reacts to exhaust
any chlorine demand present in the water
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
Chloramination Curve
• Continue to add chlorine to the water– After chlorine demand is exhausted, chlorine
reacts with ammonia to form monochloramine
HOCl + NH3 NH2Cl + H2O
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II
5:1 Cl2:N Ratio
Chloramination Curve
• Continue to add chlorine to the water– After complete formation of monochloramine,
monochloramine reacts with additional chlorine to form dichloramine and nitrogen trichloride.
HOCl + NH2Cl NHCl2 + H2O
Chloramination Curve
• Continue to add chlorine to the water– As dichloramine and nitrogen trichloride form,
the addition of chlorine continues to oxidize these compounds to nitrogen gases
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II
Breakpoint 9:1 Cl2:N Ratio
IIII
5:1 Cl2:N Ratio
Chloramination Curve
• Continue to add chlorine to the water– After the breakpoint, all chlorine added to the
water remains as free chlorine– Breakpoint chlorination
Cl2 + H2O HOCl + OCl-
Chlorination Curve
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II
Breakpoint 9:1 Cl2:N Ratio
IIII
5:1 Cl2:N Ratio
Free ChlorinationFree Chlorination
IIIIII
Chloramination Goals
• Complete formation of monochloramine (stay in section I)– 3-5:1 Cl2:N optimal feed ratio
• Avoid dichloramine formation– Avoid taste and odor problems
• Minimize un-reacted ammonia– Control biofilm and nitrification
Chloramination Species
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II IIII
Free ChlorinationFree Chlorination
IIIIII
Total Chlorine
Free Ammonia
Chloramination Species
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II IIII
Free ChlorinationFree Chlorination
IIIIII
Total Chlorine
Free Ammonia
Monochloramine
Chloramination Species
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II IIII
Free ChlorinationFree Chlorination
IIIIII
Total Chlorine
Free Ammonia
Monochloramine
Free Chlorine
Chloramination Curve
• Continue to add chlorine to the water– The point at which all dichloramine is
converted to nitrogen gas is the breakpoint.
Where Am I When Total Chlorine = 3mg/L?
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II IIII
Free ChlorinationFree Chlorination
IIIIII
I Am Here!
Chlorine Added
Chl
orin
e M
easu
red
ChloraminationChloramination
II IIII
Free ChlorinationFree Chlorination
IIIIII
Mono = Total Cl2Mono = Total Cl2
Free Am > 0Free Am > 0 Mono < Total Cl2Mono < Total Cl2
Free Am = 0Free Am = 0
Total Cl2 > 0Total Cl2 > 0Mono = 0Mono = 0
Free Am = 0Free Am = 0
Ammonia/Monochloramine Relationship
0
0.2
0.4
0.6
0.8
1
1.2
0 2 4 6 8 10 12
Chlorine Dose, mg/L
Mea
sure
d, m
g/L
Results as NResults as N““tt--NHNH33NN””
NHNH22Cl (N)Cl (N)
ff--NHNH33NN BreakBreak--pointpoint