Transcript Chloramination

Chloramination
On-Line Chloramination Monitoring
and Control
Scott Kahle, ASA/ChemScan
What are Chloramines?
 Chemicals that are formed when chlorine and ammonia
are combined in water.
 Monochloramine (NH2Cl)
 Dichloramine (NHCl2)
 Trichloramine (NCl3)
Benefits of Chloramine
(compared to chlorine)
 More Stable
 Less Reactive (reduced THM formation)
 Longer Lived Residuals
 Effective Secondary Disinfectant
 Minimizes Objectionable Taste and Odors
Monochloramine is the Desired
Form of Chloramine
 Most Stable
 Least Reactive (Reduced THM Formation)
 Least Taste and Odor
Chloramination Breakpoint Curve
Optimal Chloramination Control Range
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
Breakpoint as Measured by
Free and Total Chlorine Analyzers



A Total Chlorine result has 3 possible locations on the breakpoint curve
Free Chlorine reacts with Monochloramine giving a false reading until beyond the Breakpoint
First Indication of Free Chlorine is AFTER Dichloramine Formation
Break-point Curve as Read on
ChemScan On-Line Analyzer
At ratios below 5:1, Total Chlorine and
Monochloramine values are equivalent
Fixed NH 3-N 0.6 mg/l With Increasing Cl2
Mono + Free Cl2
Total NH3
Total Cl2
Calc. Dichloramine
Free NH3
Between the ratios of 5:1 and 8:1, Total
Chlorine is greater than Monochloramine as
Dichloramine is formed
3.5
3
At ratio greater than 8:1, Free Chlorine is
present
2.5
mg/l
2
At ratios below 5:1, Total Ammonia remains
constant as Free Ammonia decreases until
reaching 5:1
1.5
1
At ratios greater than 5:1, Total Ammonia
decreases and free ammonia is near zero
0.5
0
0
1.67
3.33
4.17
5
5.83
-0.5
Actual Cl2:N Ratio
6.67
8.33
10
Breakpoint with Fixed Cl2
Mono Cl2
DI Cl2
Total N
Fixed Cl2 3.0 mg/l
Varying NH3
Total Cl2
Free NH3
3.5
1.2
3
Cl2 mg/l
2.5
0.8
2
0.6
1.5
0.4
1
0.2
0.5
0
0
0
1.9
3.9
4.8
5.8
Actual Cl2:N Ratio
6.7
7.7
8.8
NH3 mg/l
1
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 small free ammonia residual
 Maintain target monochloramine
ChemScan Chloramination
Analyzer Advantages
 Multiple Parameter Analysis
 Multiple Sample Line
 Fast Analysis Time
 Benign Waste Stream
 Non-Clogging Sample System
 Auto Zeroing and Clean
Benign Reagents
 Sodium Hydroxide (NSF Std 60 Certified)
 Sodium Hypochlorite (NSF Std 60 Certified)
 Sulfuric Acid (NSF Std 60 Certified)
 Potassium Iodide (NSF Approved)
 Hydrochloric Acid (NSF Std 60 Certified)
Summary
 Chloramines are Effective Disinfectants
 Monochloramine has Least Odor and Taste
 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
 Effective On-Line Analysis Equipment will Aid in the
Control of the Chloramination Process
Chloramination
Installations
Toronto, Ontario
La Mesa, CA
Zefferhills, FL
Houston, TX
Hayward, CA
Blacksburg, VA
Hillsborough, FL
Oakland, CA
Hudson, FL
LADWP, CA
Houston, TX
LADWP, CA
Blanton, FL
Houston, TX
San Francisco, CA
LADWP, CA
Washington, DC
Houston, TX
Coalinga, CA
Hillsborough, FL
Fremont, CA
Elsinore Valley, CA
Airport Road WTP
Alvarado WTP
Pasco County S.E. WTP
Bilma WTP
Skywest Pump Station
Blacksburg WTP
Hillsborough WTP
East Bay MUD
Pasco County Autumn Oaks WTP
Stone Canyon WTP
HC Mud286
Santa Ynez WTP
Pasco County Blanton WTP
Malcomson Rd. WTP
Hecht-Hetchy Sunol WTP
Green Verdego I WTP
Dale Carila WTP
Heatherlock WTP
Coalinga WTP
WTP/Blend Stations
Alameda County Water Dist.
Inland Valley Pump Station
ASA Analytics
Chloramination
Presentation